This username is clearly inappropriate for this site (or really any other, frankly). Normally I would flag one of the user's posts, but they don't have any; is there a way to flag a user profile directly? If not, what should one do instead?
Admittedly, one possible response is that in a situation where the user hasn't made any posts to flag, there's no reason to feed the troll by even acknowledging their profile. However, I don't personally agree with that as a universal (and in particular I don't buy it in the specific situation above).