They're not actually designating anything; just retorting the story.
The only group that's really %100 in the wrong here is the Romans that enslaved/drove out the Jews and caused problems for everyone else.
Really, you're right; it was a very long time of people settling in the area before the Jews returned. Grandmother's grandmother's grandmother and such lived and loved there; they made home there.
Personally, I think the UN is kind of to blame (as far as pointing fingers goes). They half-assed the solution; they failed to consider the outcome of their decision to force a country into existence where there's already people. They looked at a bunch of immigrants and told them to go back to their country; wcgw?
In any case, estimating guilt isn't really a solution. Deciding one side is bad isn't enough here; there will have to be some kind of real resolution or it'll just be mass carnage in one way or another.