For one his face is a guy's face, the hair not so much, but it would be if it wasn't purple.
The body structure is male because there isn't any feminine curves displayed.
He is in a manly pose btw lol!
Also, I think the only thing misleading is his short shorts and his light green uniform. Some guys like that, I do not, but to each his own.
At least it is not as bad as that one guy in Naruto around the Bridge part that looked and sounded like a girl but wasn't.
The name does sound odd as well.
Now here is from the anime/cartoon, his face is a guy's face just the hair is very misleading. Honestly the people that think he is a girl do not spend much time around people. If he was a girl he would have curves like:
Although this only shows the girl trainer near the right side, she is about the same age, maybe younger than Bugsy. If Bugsy was a girl he would have a slight slope on his sides and minor cleavage.
I hope I cleared all of your confusion, if not attack a few more times and it should ware off just don't hurt yourself in the process.