Excellent post on an important topic. It's interesting that you say you found your friend's partner "creepy as hell", because one of my best friends from school was physically abused by her husband a few years ago, and when I first heard about it, I was astonished because he seemed like such a lovely guy - friendly, chatty, a good listener, and not in the slightest bit lecherous. When my friend invited us round to dinner for a girls' evening, he would cook, serve our food and then obligingly disappear. We all thought she'd found the perfect man.
When I first heard that he'd hit my friend, I thought it was a one-off and that he must have snapped due to stress. Then it happened again, and again. Eventually she left him.
She had met this man through a friend who was married to his relative. It turned out that this friend had been abused by her husband too, and he had also been sexually abusing their daughter, who is very psychologically disturbed as a result. I've never met the other friend's husband, but I know that both men are from a well-off family, well educated, and both have very good jobs - which shouldn't really be a factor, but people who haven't experienced this kind of thing tend to think it happens in families with chaotic lifestyles, maybe as a result of stress and/or alcohol and drug abuse. We try to rationalise it.
I'm glad that both of my friends got out of those terrible relationships.