Hey there,
I can relate to your situation, been at that exact same spot in the past... I´m a pretty peacefull guy and if possible I avoid confrontation, try to defuse the situation, unless is one of those situations where ppl are pushing some specific buttons, then i tend to go into tunnel-vision mode and that is usually enough to defuse the situation. But still is not a good situation to rely on that alone, I think you should definitelly go and train some fighting skills, the confidence you get from that alone can go a long way in avoiding you getting into fights, it may seem a paradox I know but its true, when you know you can handle yourself you really dont have much to prove, so I dont think that if you are a peacefull person to begin with developing fighting skills will make you a violent person, just a more secure and confident person.
There´s really not many valid reasons to get into a fight to be honest, fights are messy things and rarely turn out like in the movies.
On a more concrete level, if you have a school near, you should try Krav Maga, its much more reality based than MMA, it has a "no-rules, no quarters given" approach, and you get two in one as you wouldnt really need to pay extra money for a gym, you learn to fight and get yourself into an incredibly fit condition.
Just a last point: one thing is guys getting confrontational with you in club settings or the like as most of them arent really willing to walk the walk, or are just drunk, another thing is situations when we´re under a real treath, thats a whole different thing and then defusing/dismissing the guy might not be an option. In one situation violence is mostly moronic, in the other might be your only choice.
Good luck for whatever you choose.