WHAT DOES "BI" HAVE TO DO WITH IT?!!!!
What you're assuming is that a professed bi male is going to attack other males and force himself upon them!!!!
Think about it. You're discriminating based
on what he might do. There are a couple of words for this kind of behavior...
Please be Honest -- with yourself, and with the other couple!
All you need to do is talk to him before hand:
"As a point of information, many people attending this party will be upset if they see a male making an advance toward another male. Even a guy massaging or deliberately rubbing another guy is a turn-off for them."
If you're really paranoid, add:
"I know you don't want to offend anyone, and you respect their squicks. I'm sure I don't have to tell you to keep watch that your behavior doesn't spoil the evening for others."
If one can can honor "ask first" and "no means no", surely a person can honor "this behavior is restricted".
I'll give you two exceptions to this:
- People ask to leave a previous affair for violating a rule (being too pushy, upsetting other guests, etc.) Cite the incident(s) for them.
- People who's honesty you have substantial reason to question. Ask if they have an alternate explanation for what raised the red flag.
While it is a private matter between you and your "guest", and you will be talking to them in private, act as if the conversation is/will be public. Some day you may be on the receiving end of an un-vite (possibly based on incorrect rumors or facts) -- think how you would feel and act.