Father Coughlin was engaging in hate speech which is illegal in most countries (the US is an exception)[1].
Advocating sedition seems like a fundamentally different thing with a lot more political implications. Normally such a thing would result in the censure of individuals, not entire classes of individuals.
The case in point was a single speaker being suppressed, not a "class", though. I don't understand why people keep trying to argue as if conservatives as a whole are being "suppressed". Most of them are still on Twitter (or here, or reddit, or...).
Parler was specific community with a specific set of inadequate moderation policies and became a center of thought for a violent community that ended up engaged in political violence. And that site, and only that site, thus became a target for broad suppression by other actors in the market.
Hate speech is not a thing. It is a falsity that dumb people accept as a form of censorship when they don't like something. There are simply things you don't want to hear and things you do. Threats right? Nope.
It is true that "hate speech laws" are limits on free speech. It is perfectly reasonable to consider any limitation on free speech to be unethical, but pretending that "hate speech" is not well defined is willful ignorance. No country has absolute protection of absolute free speech.
This seems to blur the lines between "hate speech is a thing" and "hate speech should be banned." They are fundamentally different questions, and conflating them invites the normative fallacy.
Surprised you're not being heavily downvoted already. (I don't agree with that, just surprised.)
I do however think extreme hate speech is a real thing, it's just misapplied to the point where anything anyone disagrees with is labeled hate speech.
Because at the end of the day, all negativity is based on hate, right? If you can't say something nice, don't say anything at all (which is a nice convenient bromide for eliminating real critical thought.)
Advocating sedition seems like a fundamentally different thing with a lot more political implications. Normally such a thing would result in the censure of individuals, not entire classes of individuals.
[1] https://en.wikipedia.org/wiki/Hate_speech_laws_by_country