great question!!!

I would call filters on relays either free will, or editorial policy. Protection of freedom of speech is primarily against government control, but as we saw in the Twitter files, the government can influence a large platform and drastically affect the conversations around an election. If the relay were the primary place where people were getting their information, then there would be a freedom of speech problem.

The advantage of Nostr is that decentralization gives people multiple options for their information such that they can move relays if they don't like how one is filtered. Therefore, such filtering is not a violation of freedom of speech.

Back when major cities had multiple newspapers, you had a similar situation for local news. Each paper had their own editorial policy, and if you didn't like one, you would read their competitor.