Just because they advocate freedom to express those ideas does not mean they advocate freedom of speech as a whole. Talking about anything not in the liberal vogue right now opens one up to a world of hurt that wasn't as prevalent even 10 years ago. Bring up being against draconian gun control and, depending on where you live and how large your social circle is, you might get a reputation for being a bunch of things you're not. I'm often seen as a conservative for bringing up the fact that violent crime in America is down, or challenging misconceptions about GMOs or criticizing Bill Nye the Science Guy(no, I'm not kidding), or even so much as questioning the accuracy of the gender pay gap statistic. Yet I have nothing in common with the kind of "conservatives" people are talking about. In fact I'd argue that almost all of my actual positions are far more liberal and progressive than that of most liberals.
The problem is that free speech of any value has to be facilitated by the likes of Facebook and other companies. If companies control who gets banned for saying something, and their goal is largely profit-driven, and the consensus is to make communication habitable for the most consumers(as opposed to actual expression of ideas beyond vapid Instagram photos), we are essentially screwed. The left is at an advantage because they have the facade of being the ones who fight for social injustice and those who are "historically oppressed", which are things that most people, including many conservatives, can't really argue against on face value; when they are handed the keys to media power, they behave just as conservative religious fundamentalists would, just with their own particular set of ideas that are not always congruent.
That is why I find the public's support of censorship, and the socially-acceptable level of vexation over "offensive" ideas, to be very disturbing. I find that I cannot even trust a large number of people who I know, and I think many people have discovered the same thing, which is why platforms like Facebook have turned into digital ghettos.
