Not without measures that would be seen as censorship. The relays would need to agree to remove events and relays that refuse would need to be removed from the network.

On an application level the applications could filter things out too, but even that would only be client side and would be seen as the apps applying censorship across nodes.

The thing is, decentralized zero-censorship platforms have been tried before and they all end the same way. Normal people leave because they get tired of muting abhorrent content and don't benefit from the zero censorship, and platforms distributing the apps pull them for failing to adhere to ToS (Both Apple an Google stores require apps to be able to moderate user-generated content for example).

The thing is, I don't think Rowan Atkinson is a complete free speech absolutist. I think he accepts that some things are too abhorrent to be allowed. I think like most sensible people he believe there's should be balance somewhere he's just not supportive of what he sees a government overreach.

I think in general people should have free speech, but I think there has to be a line, which is usually defined in law. If we want more freedom of speech we should challenge unjust laws as Rowan Atkinson did. I don't think that platforms that simply ignore all the laws and try to help people get around them help the situation at all.