Censorship and sanctions are less preferred because:
1. They create even more distrust and encourage conspiracy theories
2. More importantly, just like journalists (who have agendas), fact checkers also have agendas. The journalism problem is solved by pluralism: having many different media platforms with different agendas allows for balance and exposure to various facts. However, due to the monopolistic nature of the social platforms, we can't have that here. What happens is that a very small number of people controls what we know and what we don't. Just imagine if Fox News was the only news platform - devastating, isn't it?
For these reasons, social media should not be allowed to decide on they're own what is fact and what is not.