>~"neither group is perfect, but it's their actual job to find and present the truth."
And let me guess, the cops' job is to protect and serve?
The situation is both more simple and less simple than that.
Journalists and scientists effective top priority is to serve their employers. Sure they want to report the news and shape truth in the same way that cops want to catch real criminals but all of these people are employed by organizations that have other priorities that take precedence.
Authoritarians hate these groups because they're effectively a competing power center. It's as simple as that. You see the same adversarial relationship between secular authoritarians and the clergy in countries with religious populations. It has nothing to do with truth and everything to do with power. Media, religious, and educational institutions power comes from shaping what people believe, truth in your words.