That guy was completely justified, IMO. I suppose we will have to agree to disagree on this.
The only excuse for violence is self defence against violence. His actions are not justifiable in any context.
To say he is justified is to endorse physical violence towards anyone who says anything you disagree with. That makes no sense.
I'm glad he was caught and that a dangerous (out of control) person is removed from the public where he might hurt others.