Free speech and censorship only mean something when the government is involved. Free speech is freedom of consequences on speech and opinion from government retaliation. Censorship is the same, it’s a tool used by governments, for the better (like censoring Mein Kampf) or the worst (like censoring LGBT books). Other than that, Lemmy instances not being run by the government, the owner is free to not want to associate with you, if your core ideas clash. You’re free to sign-up on other instances if you don’t like the ones you’re on, or even setup your own.