If you smell shit, check the floor. If you constantly smell shit, check your shoe.
Different instances can handle moderation in different ways. If an instance becomes problematic, it can also be quarantined from other instances. These 2 combine to both allow free speech and prevent poisoning of communities simultaneously.
There is nothing to stop you creating a moderation free community. You can even be part of a whole sub-federation of instances with that mindset. The only thing others can take from you is the ability to reach into their communities. It just turns out that most people don’t want to be involved in that sort of community.