Stars can do whatever they want. I'm not suggesting that they can't.
But seriously RD... think of when you're at the casino. People curse and say "bad things" all the time without punishment. Just like the floorperson at a casino can make a judgment call (if any!), I think Pokerstars should review the chat and administer the ban as necessary.
Examples: (Not politically correct, so don't be offended...)
NIGGERS SHOULD DIE <-- ban chat for awhile plz
CRACK NIGGA! <-- few days for being an idiot
I dunno, whatever.