How about none of the above?
Let's review the historical record:
-Around the end of WW1, the Greece and Turkey conducted a mutual population exchange, expelling their respective minorities to go live in the other country.
-The Arab countries de facto consented to such an exchange with the Jewish state of Israel when they expelled their Jews, who for the most part went to Israel. Under the circumstances it would've been fine for Israel to do the exact same to its Arabs.
-Israel didn't. Instead, they effectively divided the Palestinians into two groups: those with Israeli citizenship, who live in Israel proper as full citizens exempted from the draft unlike the Jewish majority, and those without Palestinian citizenship, who have the Palestinian territories as their homeland.
-If there are Palestinians who live abroad and aren't allowed to return to Palestine or integrate into their new Arab home countries as full citizens thereof as opposed to refugees, then that isn't Israel's fault.
-If the Palestinians living in the West Bank and the Gaza Strip find it too densely populated, then the fault lies with: (1). too high a birthrate; or (2). their refusal/inability to immigrate. None of this is Israel's fault.
-Gazans have lived under blockade these past 16 or so years because they elected Hamas, who've fired untold thousands of rockets into Israel with the aim of indiscriminately killing a maximum number of Israelis. Whether or not these rocket attacks are thwarted, due to Israel spending money and effort on self-defense, doesn't make them less liable for the damage the rockets would've caused, and sometimes do cause.
-The Gazans' refusal to oust Hamas is collective consent to the blockade, and whatever retaliation Israel may render from time to time for said rockets.
-If the Gazans cannot oust Hamas, then the only way to resolve the situation is for Israel to remove Hamas by force, which is the exact contingency in effect right now.
-Because Hamas uses the Gazans as human shields in their war against Israel, either blatantly (e.g. rockets in hospitals) or tacitly (they're hidden somewhere in a densely packed urban landscape), they alone are responsible for Gazan fatalities so long as Israel's aim in conducting strikes is to kill Hamas militants and civilian deaths are an accidental byproduct of that effort. An exception can only be made if Israel knows with high certainty there's no only civilians in a building and they choose to blow it up anyway, but I don't know of any cases where this happened.
-I will concede that Israel has denied West Bank Palestinians the ability to live in the large majority of the West Bank's area. This is the one concession Israel's morally obliged to make, and the one respect in which they can be labeled the bad guy.