Few days ago this user https://unix.stackexchange.com/users/77704/fucklinux add an answer which show his hate for Linux in a very rude way: I have flagged his answer as a rude one, and the answer was deleted immediately , but what bother me is this user still in this site even if his name is rude and offensive too :f***linux, I have tried to flag or report this user to a moderator but I couldn't do it, what should I do in this situation?
You can simply flag one the user's posts for moderator attention, chose "other (needs ♦ moderator attention)" and explain why you're flagging. We'll have a look
You can also, as you have done, bring it to meta. If you do, try to avoid naming specific users unless it's an extreme case like this one.
As for the user, they didn't post anything else in the few days since that "answer" so I have deleted the account.