Both kinds of statement can be controversial or unpopular. But only a normative statement can rightly be judged to be evil.
Therefore, a normative statement is the only kind of statement that can justly be subject to censorship or moderation of any kind. Descriptive statements are not politically relevant except (in the case of a forum) off-topic rules, rules against personal attacks, and other rules meant to keep things sane.
This is not to say that I think all politicians (online or offline) are obligated to follow these principles. Merely that I consider these principles to be how a space ought to be governed, especially if it is a debating forum, and especially if it is a geographic polity such as a country.
Use your imagination