I want to address two things here: Big Tech deplatforming the Parler social network and also deplatforming conservative users including President Donald Trump.
Regarding Parler, we need to make something very clear: Parler has always banned threats of violence and incitement to violence. The excuse for de-platforming Parler is that the social media platform has not effectively moderated objectionable content, but no social media site of any size can screen for everything. There is a ton of objectionable and outright criminal content on Facebook. In fact, Facebook’s content moderators have been psychologically traumatized by the horrific content they screen as part of their jobs. (See here and here and here.) The same thing happens at Twitter and YouTube.