Interesting points, but they merely hint at the underlying cause.
Liberals suffer arrested development.
Feminism is stuck in the third grade, where all boys are yucky.
The broader left suffers the insecurities of high school, desperately wanting to be part of the in-crowd.
There’s nothing truly funny about John Stewart. He semi-smirk is merely a signal for the cool kids to laugh.
At first, the followers don’t know why they are laughing; over time it becomes a conditioned response.