Similar to a "horse whisperer", one who has an uncanny ability to communicate with and train wild horses. This term applies to someone straight or gay who without much effort can lead closeted gay men or women into coming out and embracing their gayness simply through their presence, friendship, and/or casual everyday conversation.
Dude1: "Hey, I am thinking about moving in with Joe. His roommate moved out and its a sweet condo."
Dude2: "That's cool, I need someone to get me better seats at the next Cher concert."
Dude1: "Er, wuht??"
Dude2; "Oh, you'll be gayer than Elton John after six months with him. He's straight but he's a total homo-whisperer! His last three roommates went in straight but are all out of the closet now."