You can have opposing sides in an encounter both be right- even if one is otherwise wrong.
An extreme example: imagine you lived during or just before WWII in Germany, and you happened to be present as Hitler was issuing orders to kill some innocent person. You would have been right to shoot Hitler, if you'd gotten the chance at that moment, and he would have been right to violently defend himself from your attempt. I would hope you came out victorious, but I wouldn't blame Hitler for shooting you in self defense. It would be silly to fault a person for that.
No one is obligated to just sit there and be killed. No one can "lose" a right, such as the right to defend yourself. Not even by violating the same right in others.
It seems odd to me when that's what I think people are advocating. It's why "resisting arrest" is such a stupid concept for a "crime". It's why I would like to see the next death row inmate who is being lead to his execution lash out and kill a few of the prison employees before being shot to death in the hallway. If you're going to die, die like a man.
Sure, I always prefer the bad guy to be the one who loses, and if I'm involved in a violent attack I'd probably rather my attacker let me shoot him without fighting back, but I could never blame him for trying.