Librarians in the United States have been moving in a social justice/progressive direction for about the past 15 years. They are also highly online and the community is prone to purity tests and the tumblr-like political drama we've gotten used to in such spaces. This is according to my partner, who has been in the field for 20 years.

I don't know the root cause, but I do know from my own experience that a librarian is a very specific "type" of customer—extremely helpful in diagnosing any technical problem, generally positive and friendly, but God have mercy on you if you step on their politics.