In trying to understand what motivates some men to gang up on women I came across this article: How coherence defines conservatism.
The article comments on the low tolerance of conservatives for ambiguity and cognitive dissonance, which is a well known and much researched attribute. It goes on to discuss the search for 'coherence', which is the opposite of cognitive dissonance.
My thinking is that this may result in the suppression of rational thought when dealing with an uncomfortable situation, and a reliance on emotion to govern behaviour in such circumstances. Emotional responses can cause people to lash out in an unpredictable way, with sometimes very adverse consequences.
That could in part explain why some men won't acknowledge when one of their rank is behaving like a sexist pig. Instead of chastising the perpetrator who they see as one of their own, the conservative men gang up and say 'He's not being a sexist pig, you are - because you said that what he said was sexist.'
The Lynch MobSuch a response is automatic in them and none of the gang members stop to think it through rationally. It's driven by their emotion and they take comfort in the fact that every member of their gang is with them against the evil outsider (the woman). It's enough for these gang members that they've resolved the feeling of discomfort by attacking the victim not the perpetrator. They regain their sense of 'coherence'. Because they view the perpetrator as being one of their own, in their mind if they chastised him they would have had to own his behaviour and their minds could not tolerate that. It would overload on cognitive dissonance.
That's no excuse of course. The human brain, including the conservative brain, has the ability to reason. It's the behaviour of a lynch mob for which there is no excuse. Lynch mobs and gangs operate like a single organism instead of operating like a group of individuals. An individual needs to separate from the mob to think independently and start to behave in a more rational manner. (In business jargon it's referred to as 'group think' and there are techniques to try to avoid it.)