Very interesting thread.
Agree with pps about this weird cognitive dissonance.
I was bullied at work by some very unpleasant men (one ringleader)
At the time, there was one new starter who was fairly supportive to me.
(He also expressed this opinion and his dislikes of the bullies to other employees who - independently and without prompting from me - said that he had done this )
I left the workplace (for other reasons), bumped into him, and (perhaps naively) made a point about thanking him for his support at the time
(as I genuinely felt grateful and hadn’t thanked him at the time, and from a practical feminist POV didn’t want him to “not be supportive” to someone else if the occasion happened again)
He made a point of telling me (politely but firmly) that he couldn’t remember ANYTHING about this situation at all. 
Of course, I wasn’t expecting a catch up counselling session - he’d been decent at the time.
But I was somewhat hurt and confused by the “gaslighting”? Especially as he seemed a fairly confident “I’m my own man” type.
I’m really not a clingy/ socially pushy type, wasn’t asking him to “do” anything, and didn’t even “name names”
- it was still like he wanted to disown his own kindness
I reckon:
(1) he had started socialising with some of the men involved and so didn’t want to feel guilty about this
( or even was worried that by talking to me it might get back to the workplace, and he’d be the guy being excluded by other men) .
It’s down to social power and feeling part of a dominant group - keeping and maintaining that status.
(2) sounds a bit paranoid but I was fairly scruffy and sporty and tired looking when we bumped into each other ?
Whereas we worked together in the summer, and I was wearing a lot of sundresses out of uniform etc.
I get the feeling to him I was only “someone to take interest in and support” if I was pretty and presenting as conventionally sexually and sociably desirable and middle class looking ?
Oppressed and crying in the changing rooms looking sexy is good feminist, cheerful and wearing a Michelin man coat is bad feminist. 
Note how all these sycophantic dudes latch onto Meghan Markle and Emma Watson when they talk about racism and feminism
but if the poor old immigrant cleaner in their office is treated like dirt, then it’s someone else’s problem.
Overall, I don’t think there’s an easy answer to this question?
I’ve met men who are very verbally “right-on”, but who are weird sexist misogynist creeps.
They never contribute much practically and, a lot of the “women’s causes” they want to help will involve young girls and sexuality.
I’m very wary of the kind of guy who, when I say I’m a feminist, is all “I agree with you 100%” - often they’re sexually desperate and would do Hitler salutes dressed in a clown costume if it got them sexual access to attractive women.
I agree men can’t share the life experiences of women (yeah fuck off LM)
I don’t think it’s worth alienating oneself from men or Othering them - we all have areas of internal inconsistencies.
I also think there’s a lot of women disrespecting and judging and bullying other women, which really doesn’t help at all.
I’m now at a life stage where I’m trying to just take every situation - men, women I meet on a pragmatic case-by-case basis (loving many but trusting few, I guess?)
And it can be lonely feeling someone close to you doesn’t “get” stuff but then loneliness is the human condition