From Palestine Today (autotranslated):
The overwhelming joy swept around the Gaza Strip following the operation carried out by Al-Quds and Al-Nasser Salah al-Din Brigades in the Israeli military expedition south of the city of Ashkelon and resulted in the injury of 67 different Israeli soldier wounded, while prevailed shock Israeli society that has not yet absorbed the painful blow.
And across the citizen Abu Rami joy of the process, saying: I invite all the Palestinian factions to walk in the footsteps of Al-Quds introduced joy to our hearts after the sadness that Uncle sector.
The Islamic Jihad supporters distributed sweets to motorists and pedestrians in the streets of Gaza City as an expression of joy with the "dawn of victory."
The West Bank territories received news of the "dawn of victory", which was carried out by the Palestinian resistance in the sector dawn today, the overwhelming joy, playing the Palestinian need for such operations, which would restore unity to the Palestinian people which is now scattered among the sector and the West Bank.
...a university student from Ramallah said that the process was actually a gift from the resistance all Palestinians in a situation experienced by the vast nation divided, the opportunity to emphasize that the resistance is unite the Palestinian people and is the only destination, and also unite community Israeli completely against the Palestinians.
He continued: "I think that this process may revive energy in the hearts of all mujahideen factions represent Bushra beginning of a new stage of resistance and struggle with the Zionist enemy. "
(Another) noted that the joy of the people this process is only an indication of the public rallying around the resistance option, every Palestinian as he said, agreed to celebrate this process.
The first and most obvious thing to note is that these Arabs are ecstatic over what they perceive as a military victory, where many soldiers were injured. The only comparable times that I can remember Israelis being equally happy over military operations - to the point of celebration - would be Entebbe, Osirak and 1967, all of which celebrated the saving of Israeli lives as opposed to celebrating enemy casualties.
Westerners need to understand that this is a different mindset. We do not celebrate enemy deaths or injuries (and in Israel's case, Israel often treats those very injuries) - but Arabs do celebrate their enemies' pain, unapologetically.
Which brings us up to the next point - why are they celebrating?
The Islamic Jihad has always taken the "high road" in the Fatah/Hamas clashes, saying that they need to unite in order to fight the real enemy. In this case, they succeeded in creating that unity, even if it is brief. They are completely invested in the destruction of Israel - it is their entire raison d'etre - and operations like these help prolong their existence. They know that one thing and one thing only unites the Arabs and that is their pure, unadulterated hatred for Israel. This attack heralds the "unity" that Palestinian Arabs never had but always talk about.
Another point is that the PalArabs are absolutely convinced that attacks like these will bring them to victory. They know intellectually that Israel will likely respond in ways that will make life in Gaza more difficult, and from past experience they know that those responses will be limited and temporary. Their psychological boost from such "victories" are far more powerful than their humiliation fromIsrael's traditional, "proportionate" responses have been.
From reading about the visceral reaction about this attack it is hard not to think about the other famous time Palestinian Arabs handed out candy to celebrate a perceived victory- exactly six years ago on 9/11. Over the years of the intifada is is abundantly clear that civilian deaths are celebrated as much as Israeli soldier deaths.
Mentally, this attack against brand-new recruits makes the PalArabs think that they can engage the IDF as real men and that is a huge ego boost. They have celebrated in their media much smaller attacks - sniping Israeli soldiers or blowing up empty jeeps, as well as the daily Qassam attacks against kindergarteners. One cannot understand the Arab joy of hurting their enemy unless one understands their bottomless feeling of humiliation at having lost wars to the weak Jews. Their egos are so crushed that any tiny feeling of empowerment is an occasion for unbridled joy.
Which brings up another reason for attacks like these. One major purpose is to humiliate the Jews the way that the Arabs themselves feel humiliated. They project their own feelings onto the Jews and they imagine that Israelis are cringing at being bested by the Arabs. They are absolutely clueless as to how Israelis think - certainly in Israel there is anger because this Qassam rocket problem has not been solved, and there will be finger-pointing and hand-wringing - but there is not a feeling of humiliation. (If Israeli felt that way, they would have already reacted the way that the Arabs would react if they had the means - with complete and total destruction of the enemy.)
The gaps in how the two sides perceive each other will not close in the foreseeable future, so it is imperative to understand the other side's thought-process. And neither side seems to be able to do that.