No, I'm not violent at all, nor do I believe that an appropriate response to being verbally provoked (either directly or indiractly) is to get your fists out. Even if they are inviting you for some good ol' fashioned fisticuffs, I've never really seen the appeal of stooping down to their level. Telling someone no and depriving them of the satisfaction of controlling your behaviour hits harder than any punch you could ever throw, trust me.
I do believe in using violence in self-defence however. Other than that, I would also get into a shitload of trouble on my course if I was ever caught getting into brawls. Not worth it.
And no, the fact that other ISTPs may engage in similar behaviour does not justify anything which you have done or will do. At the end of the day, only you are responsible for your actions and it's going to be you alone who has to speak up for them.