Aggressive white knights?

So after seeing the post u/justlurking1608 this prompted me to post this. So friend 1 went to a club with my other friend 2 a few days ago. My friend 1 tries to help my friend with this girl by being a wing man. She turns him down (friend 2) and my friend asks why, she then said he was ugly and friend 1 gives her the finger (she was interested in friend 1 though).

They walk off and then she starts eye fucking friend 1 and then he goes back to talk and he says sorry. Then some white fucking knight comes out of nowhere and grabs his arm and friend 1 says don't touch me. My friend looks away and this guy king hits him and landed probably 6 punches in a few seconds on him.

Now friend 1 is 6'4 and isn't in bad shape. This little guy was 5'7 and wasn't bulky. My friend ended up with 6 stiches, multiple teeth lost and a busted nose for life. My friend has done boxxing and can fight but he was so shocked.

The guy who assualted from friend will end up in prison most likely as the police were called. This guy didn't know those girls and attacked my friend because he tried to be a hero.

My question is, what is up with guys like this? My friend now is very upset and is off work for multiple weeks and is in a lot of pain. It really pisses me off.