Is there really such a thing as "mainstream" anymore? What I think the Internet has done is allowed many, many microcosms to exist -- and exist in ways that are often unknown to the vast majority, even if they are extremely big in their own sphere.
In music, I have heard "who?" reactions from folks reacting to news about artists as well known as Avicii and One Direction. And it's true: if you don't follow any of the worlds they represent (stadium-style EDM and teen pop), you wouldn't have a clue who they are.
This, I feel, is more of how entertainment choice has expanded so rapidly. You are no longer limited to three channels of TV and a handful of radio programs. People thus gravitate to more specific niches that suite them. Therefore, you can both be enormously popular in your own niche and be quite unknown outside of it.
I would argue that the "true mainstream media" of the Internet has nothing to do with politics at all (eg, it's funny memes, cute pics, music and other general entertainment, etc.), and even within this mainstream, there's a lot of microdivisions. So is it surprising that specific right-wing political commentary is just another niche? (Political commentary as a whole is a niche.)
That's not really non-representation and silencing. It's more like we live in a world of niches, and increasingly you don't hear much of the niches beyond your sphere, because there's already an overwhelming amount of material in the niches you like already.