He started changing before that - it was around the time he made his movie and wanted to become a movie start. The Hollywood liberal mafia told him how it was, and if he wanted to do business in that town, he had to buy into the liberal dogma.
It started out with him being more pro-gay and he recently came full circle when he decided that he was now against the death penalty.
"It started out with him being more pro-gay"
If that's when it started, wouldn't have been the beginning? He was always a libertarian -- just like the South Park guys.