Meh. I blame the GOP more than I blame internet-based filter bubbles. The biggest filter bubble of all is still the 800lb gorilla that is Fox News. I would say that social media has given me a pretty good idea of what bullshit the right is peddling in a way that I never have before. I have to assume the other side has the same access to what I'm reading. The question is more one of why we've collectively decided that it's normal to just believe whatever set of facts, actual or alternative, that supports your worldview. If it were just filter bubbles it would cut both ways. I'm not saying there aren't simple minded idiots on the left--there are plenty of them--just that this is a one-way problem that has been allowed to metastasize on social media, but predates it by a ways.