You can't be banned from Mastodon, you can be banned from a particular instance, if the mods decide you have violated their instance-specific terms of service.
More effective content moderation was one of the primary design goals of Mastodon, designed to cater to users who absolutely don't want to read posts from users with conflicting view points. That's just the history of the protocol.
In your case, maybe your first post was about how great Macs are, but you had signed up on an account from @pcusers.social, who knows...