Even better would be if there were user-configurable "lists", whereby you could decide upfront what you want / don't want to see (like many sites do right now with NSFW content) - the default filter would be very "protective" (no porn, no violence, no gore, no hate speech) but users could turn off any or all of these "filters". The next step is the addition of user-curated "lists" / "filters" (e.g. "no democrats", "no republicans", "no vegans", "no dog lovers", ...).
edit: Adding a bit more, the people being bubbled away will likely tend to just isolate. You might think you like that idea, but having spent some time in isolation, I will attest that it kind of messes with your head. You lose your "phase lock" with society on a lot of different norms, small and large. The stereotype of the "dangerous loner", though not always fair, attests to this reality.
If you want to keep someone as a useful member of society and not a tragedy-of-the-day, you have to keep talking to them.
And by freedom of speech and thought, how about for twitter? Arent’t they a private company?