I don't think these concepts are comparable. My First Amendment rights cannot be violated by a private website, because I can always go to another website, or start my own. Being deplatformed isn't the same as being silenced, because nobody is preventing you from speaking, or punishing you legally for what you have said.

My Fourth Amendment rights could absolutely be violated by a private website, as they could hand my potentially incriminating private data over to the US authorities, without a warrant and without my consent, and there's literally no opt-out or recourse for me if that data is then used against me by the government.