Many years ago I was on a committee for a community thing. One of the other members of that committee was groping women, sleazing on them etc. The rest of us ran interference to get the younger ones away from him. At the Christmas party, I was out for a smoke and he came out to show me his dick.
I made a complaint to the rest of the committee, we discussed it at length and I was told "[Name] is a good bloke, he does a lot for the group" and "I dunno, I've never seen it".
These two men told me that 1. It's not really a problem and 2. He was a good bloke so there wasn't any point rocking the boat.
So no, not all men, but enough men excuse their mates that it might as well be all men.
"He's a good bloke, he wouldn't"
Except that he did.
Also, just because he never does it around other men doesn't mean he never does.
It sucks to hear your friend is a creeper, I know. But it sucks more to be told it doesn't matter.