How would you react if a random woman punched you in the face after a hostile verbal exchange on some street?

This happened to my friend (she was like drugged up and came up to him looking to start problems) and he punched her right back and the police arrested her but it was more so bc she was obviously under the influence of something. He did not call the police someone else did bc she was starting "problems". He thought this was the right response bc he said he is not going to simply take being punched in the face by somebofy and not do anything back and somebody perceived as more vulnerable by society (woman, even pregnant woman, guy in wheelchair etc.) should know better than to put themselves in a compromising position and start something with someone stronger. He also said you don't just get a free pass to go around hitting people bc you are a woman or guy in a wheelchair and they are not going to do anything back bc you are a woman or guy in a wheelchair etc. . My friend is also not a violent person at all and this is so out of character. I feel like he just did it bc he felt it was right. I don't know how to feel about this.