Rather different, actually. If I decide your inbound SMTP mail is spam, I can block it. Ditto for blog comments, XMPP contact requests, or really most any protocol in use on the public Internet b/c of course there will be griefers and spammers and all kinds of bad out there and we need tools to filter and protect against it.

You have the right to say anything you want (though not without consequences). Conversely, I should have the right to literally not see/hear it once I've decided it is causing me harm.

Claiming that your platform/protocol makes this impossible just sounds naive at best and nefarious at worst to me.