That's what I understood was the working agreement that Assad and his father implemented for decades operating essentially in a secular manner, and only violently opposing Israel and the Muslim Brotherhood.
Now they've got Obama Arab Spring "Democracy" where everybody kills and rapes their neighbor, and tries to be the pawn that starts WWIII.
Breaking this agreement by the Kurds will not do anything good for them and will endanger their enclave in Aleppo.
As for Israel -- I'd not call this "violently opposing Israel". :P Let me call this "violently verbally opposing Israel" instead. The border was almost totally quiet for 40 years. Furthermore, about 5 years ago there was a prepared peace treaty (Israel returns part of the Golans but keeps the strategically important heights); this agreement was killed by Mr. Obama.