(Trigger Warning, natch).
1. Over at Medium, here's a superb piece called When You're Friends With a Rapist.
2. If you're not like the social circle described in that piece, if you decide that it's okay to invite the rapist to gatherings or into your home, you are sending a really fucking significant message to the entire community. And it's a message about yourself. Yes, that person might be fun, or pretty, or the only person you know who can bartend at your party/accompany you to a show/help you move that heavy desk. They might even be funny and a great addition to the conversation. It sucks to lose that. But if you really think that what you'd lose by excluding a rapist is more than the sheer fucking humanity you'd lose from not doing so, you might want to look real hard at yourself in the mirror.
3. See also, the Geek Social Fallacies. Note that predators (and assholes in general) rely on them.
4. While I'm at it, see The Missing Stair, although I can't imagine that anyone hasn't read that one.
5. Because afternoons shouldn't be entirely ugly, here's a picture of our new-to-us cat, a member of the household for about 2 weeks now.