I don’t think that graduate school attracts lefties, I think the screening process leaves lefties in command of the field.
To get to post graduate education you have to run a phalanx of leftie professors who give you lesser grades if you disagree with their leftist social views or Marxist agendas, and then you have to be accepted into a post graduate school and sponsored by a professor in the field you want to get your post graduate degree. Then your dissertation has to pass muster with the professors on the committee that reviews dissertations and pass your ‘orals’.
Looks like it’s probably pretty stacked against conservative leaning students.
There is much truth in what you say. Many professors who are advisers to graduate students treat them badly. There is little the graduate students can do. 30 years ago, I saw a professor (himself foreign born) treat foreign graduate student almost like personal slaves. I only received my masters because I recorded the man brag about how I would never get my degree because I was "unloyal" to him.
I believe that there are schools where conservatives have a chance, such as Texas A&M.