Jews are the only people who must be ethnically cleansed under "international law"

Human Rights Watch gives an overview of forcible transfer as a crime against humanity under international law (in context of forcible transfers of ethnic populations from northern Iraq):

The forcible and arbitrary transfer of populations--that is, without any grounds permissible under international law—has been defined in the International Criminal Court statute as a crime against humanity.30 Although the crimes described here occurred prior to the ICC statute’s coming into force, and Iraq in any case is not a party to the statute, the statute itself is considered to reflect customary international law.

Prior to the coming into force of the International Criminal Court (ICC) treaty, international criminal law sometimes did not distinguish between the crime of deportation, defined as “the forced removal of people from one country to another,” and the crime of forced population transfer, defined as the “compulsory movement of people from one area to another within the same State.”31 Deportation has been recognized as a crime against humanity in each of the major international criminal instruments prior to the ICC, including the Nuremberg Charter, the Tokyo Charter, the Allied Control Council Law No. 10, and the statutes of the international criminal tribunals for the former Yugoslavia (ICTY) and Rwanda (ICTR).32 The long-standing definition of “deportation” as a crime against humanity included the crime of forced population transfer within a state’s borders.33

The Statute of the ICC, which came into force on July 1, 2002,34 includes among its definitions of crimes against humanity “deportation or forcible transfer of population.” According to one commentator, forcible transfer was specifically included “to make it expressly clear that transfers of populations within a State’s borders were also covered.”35 The crime of forcible transfer of populations includes “the full range of coercive pressures on people to flee their homes, including death threats, destruction of their homes, and other acts of persecution such as depriving members of a group of employment, denying them access to schools, and forcing them to wear a symbol of their religious identity.”36

Human Rights Provisions Relevant to Forced Transfer

Article 12 of the International Covenant on Civil and Political Rights (ICCPR), to which Iraq became a party in 1971, establishes that everyone shall have “the right to liberty of movement and freedom to choose his residence.”46 The freedom to choose one’s residence incorporates the right not to be forcibly moved.47 Restrictions on movement and choice of residence are permitted only when provided by law and for reason of “national security, public order (ordre public), public health or morals, or the rights and freedoms of others,” and such restrictions must be consistent with other rights recognized in the ICCPR.

“Ethnic Cleansing”

Ethnic cleansing refers to the policy of “rendering an area ethnically homogeneous by using force or intimidation to remove targeted persons or a given group from the area.”48 Ethnic cleansing is not defined in any international criminal convention or under customary international law, but it is a concept that is “culled from the Yugoslav conflict, where the term has been used by the Serb leadership in connection with their military campaigns to cleanse territories that are intended to be part of ‘Greater Serbia.’”49 Ethnic cleansing is similar to forced population transfer, but involves an additional element of the use of “terror-inspiring violence.”50 The United Nations has repeatedly characterized the practice of ethnic cleansing as a violation of international humanitarian law, and has demanded that perpetrators of ethnic cleansing be brought to justice.51

This is just the tip of the iceberg. Since the 1949 Geneva Conventions the idea of forcing a group of people to move out of their homes against their will has been considered as heinous a crime as possible - a crime against humanity. Here is the ICC's list of crimes against humanity that to show the seriousness of this crime:

• murder;
• extermination;
• enslavement;
• deportation or forcible transfer of population;
• imprisonment;
• torture;
• rape, sexual slavery, enforced prostitution, forced pregnancy, enforced sterilization, or any other form of sexual violence of comparable gravity;
• persecution against an identifiable group on political, racial, national, ethnic, cultural, religious or gender grounds;
• enforced disappearance of persons;
• the crime of apartheid;
• other inhumane acts of a similar character intentionally causing great suffering or serious bodily or mental injury.

By any yardstick, forcing a population to move out of their homes against their will - whether between international borders or within them, whether in wartime or in peacetime - is considered a particularly heinous act.

With one exception: forcing Jews to move out of their historic homeland in Judea and Samaria.

Doing that is not only allowed, but demanded, by the United Nations. From UNSC 465 (1980):

The Security Council....calls upon the Government and people of Israel to ...to dismantle the existing settlements and in particular to cease, on an urgent basis, the establishment, construction and planning of settlements in the Arab territories occupied since 1967, including Jerusalem;

I think that dismantling thousands of homes fits under the definition of "coercive pressure" to leave.

So as many as 600,000 people are the exception to the rules against ethnic cleansing and forced transfer.

And every single one of these exceptions is a Jew. (Arab Israelis who moved across the Green Line would have a choice as to whether they want to stay or not, but Jews wouldn't.)

As far as I can tell, no other population of anything close to that size has ever been told that they must move under international law. At worst, some sort of compromise is searched for to avoid the heinous crime of forced deportation and ethnic cleansing.

Except for Jews in their historic homeland.

The reason must be that the "illegality" of the settlements is worse than the crime against humanity of forcible transfer of hundreds of thousands of people.

From a purposeful misreading of the Fourth Geneva Convention rule that was meant to stop the forced transfer of civilians into occupied territories, over the years the international community - prompted by the Arab states demands and sometimes blackmail - has slowly changed international law, and the interpretation of international law, to make the establishment of Jewish communities built by people who voluntarily moved to the land of their forefathers into a worse crime than that of forcible transfer and ethnic cleansing. It has been a slow process but the spirit and intent of the Fourth Geneva Convention has been completely replaced by a new set of rules that are specifically and deliberately aimed at Jews.

HRW, in the paper cited above, has far more concern about the people who illegally moved into the areas that were ethnically cleansed of Kurds and Assyrians than any human rights group has ever stated about the Jews of Judea and Samaria that they want to transfer:

The Iraqi government has brought ethnic Arab populations-some also against their will, others with financial incentives-to Kirkuk to advance its "Arabization" drive, and many of those ethnic Arabs now live in the former homes of displaced persons. The right to repossess private property must be balanced against any rights these secondary occupiers may have in domestic or international law, using impartial and efficient procedural safeguards.124 In Bosnia, property claims administrators have attempted to resolve these disputes in a manner that respects the rights of the first possessor as well as the secondary occupier.125

So under the joke of "international law" as interpreted nowadays, the people who move into the actual houses of those forced out have more rights than Jews who have built the vast majority of their homes on public lands. Even Jews who were born in Judea and Samaria have no human right of staying in the homes that they have lived in all their lives. This interpretation of international law is unique to Jews  - not Israelis, but Jews. The paper quoted above bends ove backwards to ensure the rights of the occupiers, but no human rights group has ever said the same about Jews in Judea and Samaria.

 Even if you say that Israel's control of land that was for 19 years illegally annexed by Jordan is illegal itself, and even if you say that it is against international law to allow (not force) citizens to move to such territory, the rights of Jews in Judea and Samaria to keep the homes they built should be far higher than the rights of Arabs to stay in houses literally stolen from ethnic groups in northern Iraq.

But no one says that. Just as no one calls for Turks who moved into northern Cyprus or Armenians in Nagorno-Karabakh to be forcibly evicted from their homes.

"Palestine" has the right to ethnically cleanse Jews from their homeland. what would be considered a crime against humanity in any other  context in any other area of the world is considered mandatory by the UN, as well as "human rights" groups.

This is just one example - although  perhaps the most egregious one - of how international law itself, meant to be universal and to uphold the highest standards of impartiality, has been subverted by people with political agendas since 1967 to target Israel and only Israel.