I really don't think the kind of people who are being abusive on Twitter stop and evaluate the race or gender of who they're attacking before they do so. There's plenty of nasty tweeting directed towards white males on Twitter. If you can prove that such people get less abuse in a scientific way, go for it.

I think the main difference is they tend not to start campaigns to systematically 'sanitise' Twitter nor claim to speak on behalf of their entire race/gender. They deal with it in different, much quieter ways.