Nah, im straight
A fake excuse to say no that makes you seem like you're too dumb to know the difference between yes and no.
Nah, I'm straight. You asked me if I wanted to eat pizza. I was just about to say yes, but then you made me say no by being annoying.
Nah, I'm straight. You asked me if I wanted to go to the park. I was on my phone. You're the one who's dumb.
Nah, I'm straight. You asked me if I wanted to go to the store. I was in the middle of a game. You're the one who's gay.