Pretty sure they're using bitches in the reclaimatory sense. Not sure if it's really all that reclaiming if you're using it in the context of worshipping a guy, but whatever.

And no one's forcing you to use Cumberbitches. Just start using Cumberbuddies, who knows, maybe it will catch on. You can't tell me that there aren't a fuckton of SJW on tumblr who would jump on the chance to use something else than the bad misogynistic slur.