which is weird no one as far as I know as issues about Gabriel? Go figure? :) I knew a Gabriel too he went by Gabe, and I don't know if he ever got the "gay" thing either.
Gabriel also has the B in the first syllable and depending how you pronounce Galen it could be Gay-len instead of say Gayl-en so it has more potential of being teased opposed to Gabriel when Gabe has the B there.
I think it is because Gabriel is more accepted and classic. Galen is a bit "out there" in the name realm and therefore people feel a need to point it out by making fun of it I guess.