Yea that's the way I would see it - they've already take a cheap shot using a weapon and they have started the fight. If I've made the decisions to stand there and fight them (which I won't, let's be real, i'm getting the **** out of there) then I'm not about to trust them when they start to back away.
The guy was still shoving Stokes everytime Stokes approach him. The guy didn't turn around and run away, then guy didn't fall to his knees and curl up. He still stood there in Stoke's face and was still putting his hands out. What if he lets his guard down and that guy swings at him?
I can see why Stokes wouldn't feel safe in that scenario and would keep going after them. I don't know anything about the Law so can't comment on how any judge or jury will comment on this, but personally I understand Stokes. Especially given he is drunk and it's all a bit chaotic and the blood is rushing around.
The major issue, to me, is how he even got into that situation to begin with. All of them really. Go out, have a drink, fine. But getting drunk enough to get into a fight? And then ending up in an alleyway somewhere with some other random drunk people? And then getting into a confrontation with said drunk people? This is a series of bad decisions, one after another. Stokes' fighting isn't the most alarming thing to me, it is the sequence of events leading up to it. Incredible lack of discipline and professionalism.