This is the subject of, possibly, the most unspoken implied homophobia out there.
When you book a massage, they will never assign a male therapist to a male client without making it perfectly clear to the client. If the client is a woman, though, you may well get a male or a female therapist without anything being said.
Fanny packs
Drinking white wine (unless paired with seafood)
Loitering in mens rooms. ANY loitering. I don't care if it's 4 seconds longer than you really needed to be in there
Posting male genetalia on internet (only exception is TP roll thread)
Watching Elliot Roger and thinking he wasn't gay