"Nuh-uh! Everyone's either completely straight or completely gay!"
"What about bisexuals?"
"They're just indecisive. Once they meet the right man or woman, they'll find their actual sexual orientation and not be at all attracted to the opposite sex."
"So if a woman who's been interested in several men dates a woman, she's a complete lesbian who doesn't like men at all, and can never be interested in a man again?"
At which point, I realize I'm talking to Joss Whedon, and forget about the argument in favor of asking for his autograph.
Context QWP, public post