The problem is it takes time to identify them and kick them out. At a large scale, there will be a constant churn of poorly managed and malicious instances getting access to the network and then not getting booted until weeks or months later.
Addendum: Yes we know that you think ml/hexbear/grad are tankies and or .world are a bunch of liberals but it gets old quickly. Try and come up with new material.
I'd argue that it actually makes it much easier not harder. If an instance refuses to moderate itself, it gets kicked out of the network.
The problem is it takes time to identify them and kick them out. At a large scale, there will be a constant churn of poorly managed and malicious instances getting access to the network and then not getting booted until weeks or months later.