Yes and no. It's a double-edged sword, in that they can clump together a bunch of SJW-friendly Mastodon instances and de-list non-leftist ones, but the open-source nature of the project means that literally anyone with the technical skill to do so can run a Mastodon instance, gather their own user base, federate with their own chosen associate instances and have whatever kind of community they want. And nobody but the server/instance owner can shut the instance down.

In the words of GlaDOS, "Nice job breaking it, hero."