Isaac Hayes, who has voiced Chef since the series' inception, has quit South Park. He has described how he cannot be associated with the attacks on religion he sees in the show. It appears, as is noted by the Reuters report, that the problem is more specific and related to the show's recent attack on Mr. Hayes' religion, Scientology.
The episode was brutal, featuring long sections describing the bizarre beliefs of Scientologists but the inclination of those who run the religion to sue those who publically question it rendered the religion a fine target for important satire. South Park is in its tenth series and Mr. Hayes has taken part in shows where entire episodes have been devoted to mocking Christians, Jews and Mormons. If there has ever been a show which can fairly use the defence of mocking all equally it is South Park. Being so selectively offended completely undermines the moral case Mr. Hayes attempts to deploy.