Why, particularly, do you think that Jewish people buying land in Palestine and acting as reasonably good neighbors would necessarily have been treated any worse than other immigrants to other places (which is admittedly not a high bar)?
Because the violence started almost immediately, and minorities aren't treated well anywhere in the Middle East, especially Jews, which even before being expelled from Arab countries, had been whittled away to a minority (similarly to Christians and Zoroastrians).
There was some lingering antisemitism before 1948, in part due to the propagation of Nazi propaganda in the Middle East as well as the Protocols of the Elders of Zion hoax, but it is notable that the massive decrease in Jewish population among Arab countries only comes about as a result of the establishment of Israel, Palestinian exodus, and the 1948 Arab-Israeli war. For comparison, in the United States before the famous attack on Pearl Harbor, there was anti-Japanese racism; it massively increased as a result of the war. Now imagine if Hawaii was the whole West Coast and rather than pushing back and eventually winning, the United States was forced to capitulate and endure an ever-expanding colonization of the lower 48 by the Empire of Japan, starting with California, Oregon, and Washington, but continuing across the continent with violent enforcement and ethnic cleansing despite popular resistance. Imagine if Seattle and Los Angeles were razed during this time. Do you think there might just be a bit more anti-Japanese racism in that case? Could people of Japanese ancestry feel safe anywhere that identified with the American struggle in such a case? No, and we would correctly attribute the animosity not entirely but mostly to the legitimate grievance. And not just in the United States, but Mexico and Canada and other members of the Commonwealth would have similar anti-Japanese resentments based on the situation of American colonists as well as what remained of its indigenous population and their treatment by Imperial Japanese colonizers.
In this analogy, the Jews would be the indigenous Americans, the Arabs the Euro-Americans, and the United States wouldn't exist, but simply be a territory that's belonged to numerous empires with numerous waves of people coming in and going out (usually by force).
Japan, here, is trying to conquer a land that was never theirs, and if Japan was expelled from the US, they'd have Japan itself to fall back on.
Also, not sure if Mexico would actually be against Japan here, but meh.
Given this, I think your assessment of the prospects of Jewish immigration into Israel is a bit silly. Why assume that, without the constant inflaming of tensions that Israel's ethnic cleansing of Palestine causes, racial conflict would get worse rather than improve somewhat, or at least not get much worse, as has happened elsewhere that there isn't such an incredibly brutal and ongoing mistreatment of one population by another?
It would 'improve,' in as much that the Jews would be removed from the land. You can't have a problem if the problem doesn't exist, so to speak.
And yet we're not looking at the extinguishing of one or another race from existence here.
First, race isn't a thing, and doesn't apply to the context. Second, no-one's being extinguished from existence. We can (and should) deplore Israel's actions in the West Bank, but as a people, the Palestinians exist. They exist to the extent that the no. of Palestinian refugees has gone up over the decades because this is the only group on Earth where refugee status is passed onto children, in part because Arab countries refuse to give them citizenship.
If the Palestinians were to somehow win the conflict, even if it were accomplished mostly under the leadership of Hamas, it is unlikely that the result would be anywhere near as bad for Jewish people in Israel as the last several decades have been for Palestinians. I think anyone can be confident of this if for no other reason than that Hamas would certainly not enjoy the same relationship with the United States as has Israel. And it is not as if Hamas's original (since revised) charter is particularly more odious than the original charter of the Likud Party except perhaps from the perspective of a Jewish Supremacist... or one who favors brevity.
Then we disagree, a victory under Hamas would be worse for Jews than Palestinians under Israel. We know this because:
-Hamas's goal is an Islamic state, and you only need to look at the status of minorities in Islamic states to see what life is like for them. Its goals go even beyond the mandates of the 1947 partition (in that it wants Jerusalem as solely an Islamic city).
-This isn't excusing Israel's actions in the West Bank, but in Israel, Arab Israelis enjoy the same legal rights. Israel is a Jewish state, explicitly, and that does come with privilages, but on the other, Arab Israelis aren't given mandatory service in the IDF, and still operate under the premise of "one vote, one person." Hamas would hardly be so magnanimous.
-Even inside the borders of the area, we can see how Hamas has run Gaza, and what Jordan did to the West Bank for Jews (expulsion of all Jews into Israel, destruction of Jewish sites in Jerusalem and other areas).
-Hamas is supported by Iran and Qatar, and is part of a wider network with the Muslim Brotherhood. Iran, in particular, has everything to gain from an Islamic state in place of a Jewish one, because it helps in their cold war with Saudi Arabia.
I listed possible solutions to the conflict above. None of them are perfect, but Hamas easily lurks at or near the bottom of possible outcomes.