Not a friendship group of 60 women. I said it was "60-40", implying percentages. The extended group is probably closer to 25-35 people depending on other halves, marriage etc, but slightly more women than men. Does that make more sense?
The woman in question was beaten exactly once, at which point she went to the police and ended the relationship immediately. There were extensive and brutally honest conversations between all of us, and I trust when the women said they hadn't been victims of abuse. One of them even confessed that she thought she "might" have been abusive to one of her exes in her younger days (not that I expect you to believe that, since you don't seem to want to believe much else that doesn't fit your world view).
Note that I'm not trying to extrapolate those proportions to the rest of the population (although they do very-roughly stack up with the statistical proportions), given that it's hardly a statistically-significant sample size. All I'm giving are actual facts based on the people I know, what I've been directly told and my own experience. I leave it to everybody else to insert fabrications and suppositions.
For what it's worth, in case you're drawing a conclusion here, I'm a woman in a same-sex relationship; the only horse I have in this race is that I care about a number of men and boys, I abhor violence and I really wish society could find a way to move forward without blaming the blameless.
As for what would help reduce male-on-male violence...I don't know, but I do know two things:
1 - Men mostly don't respond to the same approaches to support that works for women. If they did, there would be more take up for men's support groups (as noted by @Brefugee ).
2 - It will likely be a fix on generational timescales; this is entirely gut feeling, but from what I've gathered and been told...the people who are violent rarely change, and usually had a shitty upbringing where violence was commonplace and accepted; that's not me trying to excuse it - simply that it seems like there's a correlation, and the results are deeply-rooted enough.
3 - As I said, excluding women from the conversation by saying "Not women's problem" won't help, because both men and women can have useful and valid things to add to the process. This is society's problem, regardless of who's to blame, so - as with most things on such a scale - society needs to change to solve it.