You can make your own Fediverse instances and do whatever you want on them, but you will get instance-blocked and you can't force them to "reason" with you about it.
If you want to exist in the company of others, you must regulate your behavior. This is not dictatorial, each person gets to say on what terms they want to deal with you or not.
If someone is posting like a Nazi, it will always be more efficient to block their messages from propagating, than to require each and every user to individually see their messages and then block them.
It depends on whether what you're about to say is "Hitler did nothing wrong." Nazis lost WWII, so the entire world is not safe for them. Nobody cares about creating safe space for Nazis.