Cultural separation serves the purpose of safety.
You coworker has been hurt by insensitive and rude people in the past. limiting his social interactions helps protect him from that pain again. At a gay bar he knows the people will understand the mores and social customs of his group; including things like separation of casual acquaintance, lover and intimate relationship partner. Your overture was misinterpreted because of cultural "diversity" - and cultural diversity lead to unhappiness everywhere it is found.
RE: Birds of a Feather Should Never Stick Together..but they do