Abbas is the kind of palestinians that americans like, but Israeli cabinet is very happy to see Abbas weakened by Hamas. Abbas and Fatah could indeed be a threat to Israel, because he could seriously mess up the relationship between Israel and US, especially when the next US administration takes over. Hamas, on the other hand, is a "safe" enemy for israel to have, since Hamas ensure that no US administration will ever be able to put enough pressure on israel to force israel to give the palestinians an acceptable deal. If Hamas didn't exist, Israel would have to figure out a way to create it.
Car bomb in Syria's Latakia kills at least seven (Reuters)
from the article: U.S. pressing Israel to bolster pro-Abbas forces in Gaza