Pete makes a great post. The problem with dishing out violence is that, unless it is a (semi) regular thing in your life, you never know how you will react when confronted with potential violence. You could fly off the handle and go berzerk, you could start shivering so uncontrolably that you are no use to anybody and everything in between.
The best way to be prepared for something like this is to be an at least somewhat trained fighter. Whether it's boxing, karate or whatever doesn't matter. What matters is that you have been in situations where there will be violence, you know what to expect when you get hit and you are more or less comfortable in that situation. Therefore you are able to keep thinking, which is a huuuuuuuuuuuuuuge bonus.
People are usually scared in a fight because of the unknown it represents. It's outside your comfort zone. Remove that and you stand a very good chance of whooping old school ass.
And if you can do the above, you stand a very good chance against the avarage junkie and chav. They usually rely on intimidation and the fear they project to do the "talking". They threaten violence, but are rarely good at it. If they run into somebody who is "comfortable" in that situation, 50% of the time they give up, 40% of the time they are sh*t out of luck and the remaining 10% is anybody's guess, but it usually makes the papers.
