That's not the point. They just don't want to think censorship is an accepted part of their daily lives because censorship often implies oppression. But censorship is part and parcel of almost every forum. The social values of the people who own the forum, as well as incentives behind their operating it, determine what kind of censorship is applied.
For example, on YouTube, hate speech [which I know isn't actually a thing] is commonplace - they don't feel the need (or perhaps don't have the resources) to censor comments which certain people find detestable. But they have created complex systems to analyze videos so that they can identify certain ones and remove them automatically. The end result is that censorship isn't applied uniformly. In one example, a YouTube account that was documenting videos of attacks on the people of Raqqa was flagged for spreading terrorist propaganda. You could make the argument that while the hate speech didn't impact their bottom line, the videos could, so they accept a certain amount of unequal and unintentional censorship in order to maintain their business position, defend their corporate values, and of course, retain their user base.
Moderation is a more nuanced and human approach to censorship. By giving people second chances, answering emails, giving the occasional explanation, etc they build social capital and prevent emotional backlash that could threaten the status of the forum. By helping users to understand the error of their ways and have a chance to redeem themselves, they can't be accused of unfair treatment. But they are indeed imposing specific social and political values on their users, to the point of hiding or removing the post or user when it doesn't align with their values. This shapes not only the quality of the dialogue, but its content. This is the essence of censorship.
To severely paraphrase 1984: "To control speech you control language, as controlling language controls thought."