The easy way to react after an act of terrorism is to feel hate towards the terrorists. I think a more appropriate response is to feel pity for them.
Pity that their mind had become so twisted that they think what they have done is good. (Didn't some famous dude say something like this once: Forgive them, for they know not what they do.)
Our thoughts have a way of becoming reality. We become what we think and we attract what we feel.
So if we want less hate and more Love, our mindset must match this. As above, so below. As within, so without.
Hate can never overcome Love, it can only make more hate. But Love can both overcome hate and produce more Love.
This terrorism problem was created by government. It is not going to be fixed by government. If you want the world to change, start within yourself first.
Peace, Love, and Liberty.