"Yet the Israeli regime has no compunction in punishing every single citizen of Gaza."

Yes, they are responding as if Gaza as a whole is guilty.... but it's hard to imagine how else they could have done it. Hamas probably knew what would happen when they planned this stupidity.
   Many Germans were against Hitler, but they were bombed too.

Electricity, water and food... and munitions.... have to come into Gaza from outside, and Israel can control most of it. Iran can't email more rockets to Hamas.

The early reports say that there has been not only murder, but savage, horrible mutilation of victims where Hamas fighters have been. This alone would cause Israel to pull very few punches in retaliation. They are trying to because they don't know where captives are being held.