I think it's a jealousy and competitive thing rather than it obviously being sexual.

You know when you see another good looking man. If it's a celebrity, i.e. someone who's far from your everyday reality, then you want to be like him, you want to emulate him so although you may not have the same physical features you'll try to pary him by adopting his dress sense in the hope that women will like you as they do him.

If its a guy who you know or is in your social circle who you know looks good then you'll obviously see him as a threat because he's getting all the attention; making you look small.