If your straight guy friend says that he supports gays, tell him that you thought he was gay when you first met him. See how fast he gets upset and insecure & starts asking you why you thought that.

My gay guy friend tried this to our straight friend and the response he got was “thought? More like hoped” and then he winked. That’s a real ally right there. 

He really just scalped your poor gay friend on the spot didn’t he lmfao

I tried this on a straight friend and he turned bright red and mumbled something about how he might be bisexual actually? so I introduced him to some of the other queer folks I know and flash forward 4 months he’s definitely bi and out to all of our friends and dating a guy on his intramural kickball team.