Spoiler alert - he was wrong.
But.... you don't actually know that? I don't know what this particular individual did but what if his attempts at kindness and empathy convinced five people to not join in on the violence, when anger and violence would have stopped none?
It's an interesting observation but I would think that if that was the case, the pattern would have been obvious to those who have been researching this phenomenon. I'm inclined to think it was not mentioned by the researchers because there is not much of a link there.But if you want to talk about what works - there have been several articles linked in this thread featuring "reformed" racists, and every single one of them including yours had one thing in common. These people have all have done jail time and it was in prison that their reformation took place.
The key thing that I see is that in our modern society, people join these kinds of hate groups out of a sense of isolation. The hate groups exploit that and give them a sense of belonging to something. Going around punching them is very unlikely to make them feel less isolated from civil society, don't you think?