A coworker of mine has recently made a series of jokes in poor taste regarding rape - an excerpt, verbatim: "It's always the right time for a rape joke" all outside of the office/work hours. He's smart enough to know that there are certain lines he can't cross when he's at work, so he usually doesn't make inappropriate comments during work hours, but that doesn't seem to mean that he actually understands why he shouldn't make those comments.
I've called him out a little over a year ago for posting a comic that inferred rape on a company-wide slack channel, and at that time, I didn't bring it up to the level of HR mediation. His response was that I didn't know how to take a joke, and it's only when another male coworker confirmed that it was inappropriate that he took it down (I'm female). Since then, he hasn't made rape-related jokes during work hours, or at the office.
He was more in check when he initially started at our company, but as he's approaching his second anniversary, he's showing more of his colors.
Typically, his conduct comes off as passive-aggressively sexist (frequently dismissing opinions from female coworkers whereas he doesn't with male coworkers, even if their opinion turns out to be wrong), and I'm wondering if all of this is stemming from the fact that he lacks respect for women.
As these are more or less private comments he made outside of work hours, reporting it feels like I'm infringing on his privacy, but privacy isn't a clause that exonerates people from criminal activity or hate speech. He knowingly made rape jokes outside of work hours understanding the boundaries so I could take solace in knowing he won't say it at work, but I don't want to work with someone who thinks violence of any nature is comical.
Should I raise this as a flag with HR?