I can't say I'm backing this argument nor am I super interested in giving her more views. I am not impressed with someone having a strong opinion without knowing what they're talking about. "I don't know anything about skateboarding, but I've heard things."
She is basically the alternative and edgy version the uptight teacher in Donnie Darko. "Fear and love are the deepest of human emotions."
Skateboarding is certainly biased towards white straight dudes, however, to claim that skateboarding is a place for the same old traditional dominant white straight masculinity is bullshit.
There is no fucking question skateboarding is an alternative form of masculinity that overtly rebels against all sorts of traditional aspects of the way men are supposed to act. Comparing skateboarding to the idealized versions of how to be a dude (the football player, the frat boy, the businessman, etc.) is complete bullshit. To borrow from R.W. Connell, skateboarding is an alternative but complicit form of masculinity. It is very very different from that hegemonic masculinity or machismo ways of being. It reinforces some hegemonic structures in society, while also offering an alternative form of masculinity and, while the social world of skateboarding has significant problems, it is way more open to various (economic, racial, gender) minorities than other social worlds that promote traditional white masculinity identities.