I think criticism of Israel is fine. What I don't think is fine is gratuitous criticism and that is pretty much all I'm hearing from pro-palestinian voices. The fact that to call for Israel to leave Gaza now is to call for Hamas to remain in power is something you don't hear people saying that out loud, even though as it stands that is the inevitable result and the outcome Hamas continues to insists on. It's almost as if Westerners in particular are protesting on behalf of some as yet non-existent entity that will miraculously surface to rule the Palestinians in a way they (the Westerners) would consider dignified. But there's no such thing. It's a typical case of mistaking the powerless for the good. I'll start blaming Israel exclusively the moment Hamas are prepared to put relinquishing power on the negotiation table. Until they do, they're at least as much part of the problem as Israel.
As for all the supposed historical justifications for what Israel or Palestine are historically entitled to, that may be interesting from an academic point of view, but I hope everyone's aware that there's no solutions to be had there. Quite the contrary.