He ended up on that site because he's different ("oh noes! A man wearin' a skirt! What's wrong with him?? Har har har!"). As someone else mentioned, that site is full of bullies that enjoy making fun of people.

I'm not at all surprised someone in a kilt (of any kind) showed up on there. Frankly, I'm surprised it didn't happen sooner. Another site I'm a member of (not a kilt site) has already gone through this and were disgusted by the comments left about someone who very well could have been a member of that community.