I'd have more sympathy for Israel if they weren't Hamas' primary source of support and funds in the 80s.
This is probably asking for a lot...but cite?
I'm not sure if Israel could be called Hamas' "primary source of support", but I also read something along those lines once... the bottomline is that Hamas was originally aided by Israel because the organization was seen as competitor and counterbalance to the PLO/Fatah. Of course, this was in times when Fatah was Israel's main enemy. Support the Hamas and weaken the Fatah. Divide and conquer.