It's not a duel with equal weapons, or an sportive match. And also, the syrians aren't in a war against their neighbours, it's between themselves (or I should say between Al-Assad and the rebels).
It's sad that a country like Syria lives this situation. But would be worse that the situation extends to near countries.
In my opinion the previous status quo was better for Israel. Now are growing terrorist groups in Syria, and beyond their rivalities, they can join to support anti-israeli actions.
Precisely the strike wasn't over the Syrian Army but against Hizbullah bases with stockpiled missiles destinated to Israel.
RE: should a change man die in a prison cell for one mistake?
For example, digging a tunnel to rob a safe-deposit box of a bank, "by mistake".