As a white male you haven't experienced any of that, which is fine! But you should try to put yourself in the shoes of people who weren't so lucky.
EDIT: I was addressing the poster directly. As a white guy with autism, I'm well aware that white males in general can experience lifelong hardship for any number of traits. But anyone who says "I don't really understand why all these groups are around race, sexuality or gender" presumably hasn't experienced that, or they'd immediately understand why someone would want to associate with folks who've been through the same shit.
(Or maybe I'm still giving him too much credit. But I try assume ignorance rather than malice.)