Mastodon doesn't have a recommendation engine really. If you're getting lots of right wing lies and propaganda, then it's because of who you chose to follow.
I would imagine that somebody who is complaining about seeing a lot of right-wing propaganda is not somebody who would follow right-wing personalities. So if they are seen right-wing propaganda, that's a problem.
Perhaps it kind of just glitches out if you don't follow anyone and just gives you anything.