I think Thompson there was suffering from buyer's remorse. His Rolling Stones article, instigated by a speech that probably lost Carter a few important friends, significantly contributed to selling the candidate to the hard left, which was large and influential at the time. A year later, I think he felt the classic sense of "betrayal of the revolution", or maybe was just trying to distance himself from the promises he had helped popularize in '76. The sort of things he said, beyond the showmanship, basically apply to any post-Kennedy politician, and possibly even the ones before: they will sell their mother if it gets them elected. In this respect Carter was not really different, or he wouldn't have been elected US President.