Arguments and antitrust lawsuit could be made against many top level domain names. Manwin Licensing, the company behind YouPorn, has sued .xxx registry ICM Registry for violating the Sherman Act (i.e. monopoly). If you read the complaint against ICM you could substitute other top level domains for .xxx and the suit would still make sense. Manwin says .xxx wasn’t put out to competitive bid, has no price caps, and ICM Registry gets presumptive renewal.