Why do people think my best friend is Gay?

My best friend is a great guy, and hes really funny and nice to everyone. The thing is, almost everyone thinks that hes gay. I dont know why, and its hurting his feelings as well as mine because people make fun of me for being around a "gay" guy. The thing is, he never acts gay, or indicates in any way that hes gay. In fact, we talk all the time about girls and he told me who he has a crush on. Also, he gave a girl at my school chocolates at valentines day, and she started crying and ran away, then someone told him later that she was embarrased because "some gay freak is creeping me". People think its a ploy to get them to think hes straight. The important thing to remember is : HES NOT GAY. im one thousand percent sure. why do people think hes gay please help