Yes and no.

It's only mob rule and authoritarian if you look at yourself and such a community in isolation. That is: when you get kicked out, you land utterly alone in a void. Much like being banished in old days from a tiny village.

But on line communities don't exist in isolation. They are embedded in a larger, complex, modern society where social identity is based on a layers of many social connections, and where your rights and freedoms are anchored in an established legal and constitutional framework. You also still very much belong to your family, close friends, work, school, neighbourhood and so on. (Unless you migrate and end up in a legal limbo; or live in a strict and authoritarian society)

Sure, you can claim authoritarian or censorship because someone isn't willing to listen to your opinion. But, depending where you live, that doesn't mean your constitutional rights in general were violated. Not by a long stretch. All it means is that a particular person or group of people are done listening to you. You're still very much free to go out and find like minded people.

You're also not entitled to admittance. Why? Because the vast majority of servers - whether that's IRC, Mastodon or Reddit - you'll join are managed privately. It means that you are a guest and your presence is allowed by the host as a courtesy. Much like you are also a guest when you enter a shop, a bar, a restaurant, a movie theater, a theme park,... The notion of private property implies that the owner - whether that's a person or a legal entity - is free to kick you off it if they feel the need to do so.

You could argue that you getting kicked out is an act of violence. But then the only entity that could conclusively assert your claim is a court of law. Any judge will verify your claim against a touchstone which is the prevailing legal framework such as it is. Since free speech only applies to the government, any claim between private citizen referring to this right won't hold in a court. Getting denied entrance or admission to a group won't be seen as violent either: private property owners have that right.

The only way forward would be to demonstrate intent in a way that you getting cancelled becomes a legal infraction: you got kicked out because of a clear, demonstrable discrimination against your identity: colour, race, creed, religion,... Which is extremely hard to establish before a court of law.

There's actually a paradox at the heart of all of this. Karl Poppers' Paradox of Tolerance. It states that a society that allows far reaching freedoms also comes with an individual moral responsibility to act tolerant towards differences between peoples. Sadly, some people will peruse those freedoms to promote intolerance and division. In order to protect freedom and basic rights, it's necessary to show intolerance against such intolerance.

The issue with this paradox is that it doesn't state where the line is to be drawn between what's acceptable and what's unacceptable. Worst case is that by being overzealous in showing intolerance against intolerance... society ends up curtailing the very freedoms and basic rights it purports to uphold.

It's exactly why it's so hard to legally assert that the intent with which you were kicked out from an on line community was discriminatory. Such a ruling needs to be extremely carefully considered as it might create a legal precedent that curtails other basic rights and leads to other, unintended, forms of legal inequality.

And so, it's important to have an ongoing debate and figure out a common moral framework to manage this conundrum. It's equally important to be activist in that regard and find well-founded arguments against ideas and beliefs that target basic human rights or outright dismiss the notion of a common understanding and respect towards fellow humans. The fine print with all of this, then, is that you have to be extremely careful not to become the very thing you purport to fight... which is exactly the kind of perception your statement about mob rule and authoritarianism risks creating.