He tries to gain credibility with "the center," by slamming conservatives every few shows -- even as he becomes wealthy for positing semi-conservative views, as in his Culture Wars ploy.
Meanwhile, his ego is quite likely stroked as he views his ratings and financial holdings.
Only people with no vision thing that there is a "center" in between a left wing and a right wing. In reality, formerly-Democrat social conservatives and mainstream Republicans are the majority of Americans, and the Democrats have increasingly chosen to represent the extreme fringes of society, from mega-weathy Hollywood and financial tycoons to the poor whom the rich use as human shields.