Their latest 100+ page report is about damage to civilian property in Gaza during Cast Lead/Operation Oil Stain.
Here is a part of the report about the Izbt Abd Rabo neighborhood:
Many residents who lived on or near Zimmo Street and who left the area between January 5 and January 12 said their homes and those of their neighbors had not suffered serious damage at that time, and that the closest fighting was at least 500 meters away to the west, beyond the borders of Izbt Abd Rabbo. By January 18, when residents returned to their homes, they found virtually the entire eastern half of the neighborhood, including scores of houses as well as hundreds of dunams of land, had been razed by Israeli forces.OK, assuming that these dates are accurate...
The finding that most of the destruction in the neighborhood occurred after the initial phase of the offensive is corroborated by satellite imagery analysis performed by the UN Operational Satellite Applications Programme (UNOSAT), which identified destroyed or severely damaged buildings in Izbt Abd Rabbo over time, based on damage visible in satellite photographs. UNOSAT found that only 11 buildings in the neighborhood were destroyed or severely damaged between December 27, 2008 and January 6, 2009, but that 330 buildings were destroyed or severely damaged from January 6 to 19 – a thirty-fold increase in destruction that occurred after the IDF had apparently established control of the area.
Palestinian fighters had launched rockets from the surrounding open areas prior to the offensive, residents said. Residents told Human Rights Watch that border observers (murabbetein) from Hamas and other Palestinian armed groups were present in Izbt Abd Rabbo frequently before the conflict, and that armed groups had used open areas nearby to launch rockets at Israel. Hashem Dahalan, 49, speculated that Israeli forces “destroyed many more houses in the eastern part of the neighborhood than the west because the fighters who came to this area in the past [operated in] the east.”  At least one house that was destroyed early in the conflict had an escape tunnel leading to another house, Dahalan said. While Hamas militants made use of the area, he added, few lived there: “Only six of the destroyed houses belonged to Hamas.” Another resident, Mahmoud Rajab Abd Rabbo, told Human Rights Watch of tunnels in Jabal Kashif and Jabal ar-Rayes, the hills to the north and south of Izbt Abd Rabbo, respectively. From residents’ accounts, Palestinian armed groups may have used some houses in Izbt Abd Rabbo as cover before or after launching rockets from nearby areas or for other military purposes.HRW is ignoring a basic fact about the operation: Hamas' major goal.
Houses that Palestinian fighters were using as cover, which concealed tunnels, or that otherwise comprised military objectives were subject to lawful attack. Residents said that such buildings constituted a very small minority of the houses in Izbt Abd Rabbo. Human Rights Watch is unaware of any evidence that could lead the IDF to reasonably conclude that more than a small fraction of the houses that it destroyed in the area could have constituted military objectives, even assuming that the IDF considered it lawful to destroy houses that militants were likely to use in future attacks (in addition to houses whose destruction was likely to yield a concrete and definite military advantage during the conflict, as permitted by the laws of war). The wholesale destruction of entire blocks of buildings, even if some could have been lawfully destroyed, would still amount to wanton destruction under the laws of war.
Hamas didn't expect to win militarily. It had one, overarching strategic goal: to kidnap IDF soldiers.
If this neighborhood hosted Hamas houses and tunnels hidden among the regular civilian residences, that meant that IDF troops who were in control of the area were in grave danger of being kidnapped.
This is a different kind of war, and HRW ignores this key aspect of it. The assertion that only a small percentage of houses belonged to Hamas is irrelevant to this scenario, unless the IDF knew ahead of time with certainty which houses those were.
The UN Fact Finding Mission on the Gaza Conflict noted that, according to an article published by an Israeli NGO, “Izbat Abd Rabbo and the nearby areas of Jabal al-Kashef and Jabal al-Rayes appear to have been among the locations in Gaza which saw the most intense combat during the military operations.” In one incident, the article stated that on the evening of January 9, 2009, “three RPG rockets and machine guns are fired against a house where IDF soldiers took up positions in the Ezvet Abd Rabbo region in the eastern sector of Jabalya.”...
Human Rights Watch was unable to determine the number of Palestinian fighters and Israeli soldiers killed or wounded in fighting in Izbt Abd Rabbo. We interviewed several residents who said that Israeli attacks killed at least six fighters in Izbt Abd Rabbo by January 6. Cross-checking lists of fatalities compiled by the Palestinian Center for Human Rights (PCHR), a non-governmental organization based in Gaza, and the Israeli NGO B’Tselem, indicates that at least four militants (all Hamas) were killed in Izbt Abd Rabbo on January 3, 12, and 18 (two fatalities).
We have no idea how much non-fatal fighting there was during the other days. However. there was clearly fighting in this area that was under IDF control during this time, and the IDF needed to be concerned about how the terrorists were hiding.
HRW is assuming that the "military advantage" that Geneva allows is traditional - destroying buildings that could be used for lookouts or for hiding weapons, for example. In this case the military advantage was to take away Hamas' military objective - which was to violate the laws of war to purposefully kidnap enemy combatants! In this case, every house in the area that militants pop up has the potential of being militarily critical.
Given that this was Hamas' military goal, the IDF is justified in neutralizing it. One could argue whether they went overboard, but given that militants were certainly in the neighborhood while the IDF was there shows that they had effective hiding places - places that the IDF was obligated to root out.
I guess HRW's military experts didn't think of this. Oh, that's right - their only military expert already left HRW.
They're just winging it.