There is no Mastodon for them to be blocked on in the sense you’re talking about.
Mastodon is similar in setup to Lemmy in that nobody owns it and anyone can run it. I am absolutely positive they are banned on tons of Mastodon servers and not banned on tons of others. If the server you are on is federated with even one server with one that isn’t banned, you could potentially see their posts, at which point you can either report those posts to your and their admins, or block them yourself.
There is no Mastodon service. Its an application anyone can download and run. I understand your frustration, but it seems like you’re mad at the universe they exist in for its role in housing them.