I don't believe I am, though--you are, if I'm not mistaken, asserting that it's some prolific iniquitous undercurrent which these platforms are subtending in some manner. (Which would seem somewhat misleading to me, as your assertion that r/TheDonald moved was of their own volition, rather than a banning by the site.)

Any platform harboring content will, as a matter of course, simply through the caprice of a moderator, let slip by insane opinions--but opining that these are some growing tide and, more dangerously, representative of their moderate counterparts (a la the r/Conservative subreddit, which seems constituted of largely by-the-numbers right of centers,) seems disrespectful to all parties involved and serves only to distract from your central assertion that communicating these ideas will in some way seed wanton chaos. (Comparing the ideas directly to those that precipitated the tragedy of the Holocaust.)

Edit, as I'd written my reply to a previous version of your own: I am sympathetic to the idea that seeing these more fringe ideals is unfortunate--but the argument which I believe bears greater importance is that acting in this manner against them, striking them from the whole of our public discourse and pre-empting any who could, in some way, divine inspiration from the muck is far more deleterious to discourse. It serves all too easily as a means to silence disquiet and cast a veneer of unanimity.