They will leave provably wrong stuff up as a head on pike to show you're an idiot. They will let correct but unpersuasive stuff up, because who cares. They will let correct (or just controversial) stuff already stated by someone prominent up (even if by kkk or nazis), because they already have a rebuttal canned for that to make you look bad.
What they won't let stand is a correct, holistically persuasive original argument for the wrong opinion. They have no defense for that but banning. And thus doesn't apply only to reddit.