For me the reason to not fight dirty is also that it gives the enemy the license to also fight dirty. When I was a kid, there was some unwritten honor code to n

For me the reason to not fight dirty is also that it gives the enemy the license to also fight dirty. When I was a kid, there was some unwritten honor code to not punch each other in the balls. Or maybe not honor, just fear of reciprocal actions. I think it made a lot of sense. It all depends on the context of course. If somebody would try to do me serious harm, of course I would kick his balls. If it is just about domination, might not be such a good idea. Even more so with scarier stuff (knives, hard objects) - this could become dangerous really fast.