I know this sounds like a cop-out answer, but as an attorney, I would zealously represent my client on either side.

I don't know all the facts here, but I do know that as a practical matter, it comes down to a whole bunch of factors, among them, use in commerce, possibility of confusion, etc. But I can say that judges take a dim view of people who tell others to "fuck off" and who appear not to have a justifiable reason for using a name nor a long history of doing so.

I also know that bullies don't always win - Nissan Computer still owns nissan.com, not the motor company.