Only in modern culture could a character be tagged as gay just because he's not lusting his ass off over every woman he sees.
Yeah Picard didn't exactly go after a lot of women, but did he go after any men? And in Tapestry it's heavily implied he was a huge ladies man when he was younger. The man is 60 and he's an introvert, and a Captain. He doesn't go after women a lot because he's withdrawn from the game.