I don't understand why so many people are hung up on the "how much is enough?" question. The question we need to focus on is "will taking action make things better or worse?" I understand that people will have different answers to that question, but anyone who isn't asking it is putting emotion ahead of reason.
I think they go together, because there's a cost-benefit analysis going on. Let's be honest. The severity of the attack does impact how far we're willing to go to make things better. We're not going to launch the next round of the Crusades over a nut shooting up a night club. As bad as it is, it just doesn't warrant paying that big of a price in money and blood, even if it would likely bring an end to ISIS and frighten other nutcases from trying to build an Islamic caliphate again.
However, suppose that instead of shooting up a night club this guy had gotten his hands on a nuclear weapon and set it off in the middle of Manhattan and killed half a million people. There's no question that most people would look at it differently, and there's no question that we'd be willing to do a lot more to stop not only the person involved but also whoever inspired him to do it. We'd be willing to do a lot more to make Islamic terrorism look less "inspirational."