I haven't been following this story carefully, but what you just said raises some red flags.
Is Paul a homo or bi?
Perverted activities among men are often violent. And, as you say, this IS San Francisco.
Was Paul getting “hammered”? I’ll let myself out now...
The more I look into this ‘radical’ group....the more they look like everyday-type swingers. I’m more likely to ask if Paul what his friendship was about. Maybe he liked the threat of a hammer-hit to the head and this just got out of hand.