The idea that land belongs to whoever settled there first is completely unworkable. For starters, in most cases it would be almost impossible to determine who that land now actually belonged to (especially in Europe) and the list of countries who would have to give back power to indiginous people would be huge. We can argue that the land should never have been taken off them in the first place but the fact is it was and that can't be undone now.
As for Isreal in particular, they may have settled there first but they haven't had control over the area for around 2,000 years (until the new state was established). After the collapse of the Ottoman Empire the land obviously had to be administered by someone after the British left but I think what gets most people so angry is that such a large portion of what was Palastine was partitioned as the Jewish state when the Jewish people were the minority in the area. Also most of those were very recent immigrants, although granted they had good reason to leave Europe around that time. The establishment of Isreal had nothing to do with granting the Jewish people an 'ancestral' home land from the Western governments point of view, it was purely a political decision.
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