I can't remember witnessing or hearing about him flirting with girls, with the exception of you talking about it. If he was flirting with girls it's probably safe to assume that he was doing it to affirm his "sex icon" status and sell more records. Like I said before, a guy singing about guys and who has guys in his videos isn't going to have as big of a fanbase as he would if he sang about girls. Do you remember girls from elementary school? How they went ape for N'Sync and Backstreet boys and Ricky Martin? They wouldn't have been so into his music if they couldn't visualize that it was them he was singing to.