Have you ever laughed at a sexist joke or meme? Have you ever had a conversation with a friend about where a woman rates on some kind of hottness or sluttiness scale? Have you ever just stood by while a guy talked about what a dog some girl was? Then you have contributed to the culture of masculinity that allows for catcalling, harassment, and rape. You don't even have to say those things, you only have to let them go uncommented upon to be contributing to that culture. Just read a great story about that. Right on point.
"Saying something like, “It’s not fair for women to lump all men together under the same umbrella” willfully ignores that the true umbrella is not men as a demographic but masculinity as a culture as it is defined in this country (and others)."