Quote from Ghost of Cutten:
Look up the definition of 'reasonable force'. Someone swearing at you, or even hitting you, does not give you carte blanche to do anything you like back to them. The law, and basic morality, permits you to respond proportionately and with reasonable force, not disproportionately and with clearly excessive violence.
A jury will decide which was the case here, after each side's lawyers have put forward the facts and evidence, and if guilty then the judge will hand down what they think is an appropriate sentence in line with their experience and sentencing guidelines. Somehow I suspect they will come up with a more considered and appropriate result than some of the emotional knee-jerk lunacy proposed on this thread.