I dunno if I use anecdotal evidence too much, but from my experience, five years ago it was possible for people to have different political views, to have a civilised conversation about policies, to agree to disagree. Now virtually everyone I know has the same political views and no-one discusses policies (you can't fit policies into a tweet, its too complex).

I think it depends on where you are; for example, ISTM that supporting animal testing, GMOs, and the like used to be pretty much taboo on Facebook in my country until a few years ago, and I would have felt very uncomfortable expressing ideas that could be construed no matter how broadly as speciesist on my Facebook wall, whereas today there is a sizeable metacontrarian current which is mostly tolerated except by extreme environmentalist wingnuts.