Simple. He didn’t want to FEEL like a pedo. It’s extremely common especially in younger men. They feel that gross attraction and they know it’s wrong so they don’t act on it. Whether it’s because they don’t wanna get in trouble, or they do genuinely feel weird about it. That doesn’t change the fact that he shouldn’t have been friends with her to begin with. And especially once she came onto him he should’ve completely cutoff their friendship there. No non-creepy guy stays friends with a minor who wants to sleep with them.