Agreed.
However, before Israel takes any action that could push Syria into a first strike, Israel needs reasonable assurance that they can meet that threat. Such assurance obviously needs to include threats from all of Syria's military allies.
Once exception to the idea that Israel cannot strike first would be a situation where it is obvious that one or more of their enemies intended to strike first, but Israel beat them to it.
There is precedent for this.
"a situation where it is obvious that one or more of their enemies intended to strike first, but Israel beat them to it. "
It needs to be VERY obvious, since Israel is already not the most popular country in the world.