My knowledge of Jewish history is basically nonexistent, but are there many of those anymore? What would happen if Jews who came to Israel after WWII tried to go back to their countries of origin? (I understand that being Jewish in 1948 Germany would have been, at best, deeply uncomfortable, though I'm not sure even that is an argument for a country in 2005.)
I'm not entirely sure what you mean by the first question. As for your second, after WWII, a whole lot of European Jews (mostly Eastern European) were in DP camps, since no one could agree on which of the Allied countries should take them in, and the British had really tight quotas on Jewish immigration to Palestine. There really wasn't anywhere for them to go.
t edit: and also, as I said, I'm not even really sure that that argument is the best one to make. I don't really think that arguing about Israel's founding is neccesarily the best way to get to solutions to today's problems.