Palestinian refugees have to stay refugees because they are stateless. Stateless refugees, unless they can find some other citizenship and therefore no longer are just Palestinian - and they often can't, must remain refugees for eternity. Since children normally inherit citizenship, that goes for their children too, until they are something other than Palestinian, nationality-wise.

And they didn't "leave". They were ethnically cleansed.

> Israel would devolve into another failed middle eastern state.

Ignoring the obvious racism here, in what sense is Israel a successful middle eastern state? It regularly attacks its neighbouring countries. It keeps 2.3 million people in a ghetto and millions others in bantustans in the West Bank. It's huge source of instability in that region and is dependent diplomatically, economically and militarily on the US.

> If Israel left them back, Israel would devolve into another failed middle eastern state.

If I let the man out of the cage in my attic my home life is going to be a lot worse. He's still a caged man though.