The great comedian raise awareness and ridicule prejudice. Chris Rock and his ilk holds up established stereotypes and says 'What sort of idiot actually thinks like this?'
That is completely different to insideous casual racism, which, whilst it might not be the intention to cause offence, and maybe no one is offended by something so banal, reinforces negative attitudes.
See a group of muslims - One of them might be a terrorist.....group of muslims - One of them might be a terrorist.....group of muslims - One of them might be a terrorist.....group of muslims - One of them might be a terrorist.....group of muslims - One of them might be a terrorist.....
If people hear it often enough some will come to believe it and this is the root cause of mistrust, prejudice, fear, hatred, 'paki-bashing' and murder, which, have no doubt has result in more people dead in the UK over the years than islamic terrorist activities.