I am a male flutist. I also happen to be gay. I wouldn't call myself effeminate, but I am the sensitive type.
The reason I chose the flute (or did it choose me?) was that one of my older cousins played it. She was the only person in my very large extended family that played an instrument. One day she let me try out her flute, and from that moment I was hooked!
There just so happened to have been another male flutist at my school a year ahead of me, so he sort of led the way. We were both accepted into the school's selective Wind Ensemble in 9th grade (the first year we were eligible). Once we got to 11th and 12th grades, we were the top two flutists at the school. I can only guess why this was so. Perhaps we were more dedicated to practicing the flute than the other (female) flutists. Maybe we just had a knack for flute playing. Who knows?
When in school, those who are different than what is conceived "normal" are always picked on. At my school, a male playing the flute was thought of as "normal" (sort of), so I wasn't picked on for that. However, I was made fun of for being in the "smart" classes, wearing "uncool" clothes (I didn't have much fashion sense), and because I wasn't good at sports (I practiced the flute instead!).
My advice? Don't worry about it! Just play the flute!