From Robert Bolt's A Man For All Seasons (substitute "principle of free speech" for "law").
William Roper: So, now you give the Devil the benefit of law!
Sir Thomas More: Yes! What would you do? Cut a great road through the law to get after the Devil?
William Roper: Yes, I'd cut down every law in England to do that!
Sir Thomas More: Oh? And when the last law was down, and the Devil turned 'round on you, where would you hide, Roper, the laws all being flat? This country is planted thick with laws, from coast to coast, Man's laws, not God's! And if you cut them down, and you're just the man to do it, do you really think you could stand upright in the winds that would blow then? Yes, I'd give the Devil benefit of law, for my own safety's sake!
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People in positions of power generally assume that they will always be in power. Many of people during the Obama presidency, wished that the president was less susceptible to gridlock between the various branches of government. In January 2016, most people never even considered the possibility that in 1 year, Donald Trump would be sworn in as President.
Right now, the progressive, center left is in a very strong position with regards to the tech industry. All the major players are sensitive to their causes, and against the alt-right. A lot of people are unhappy that the current norms of free speech are causing the social media companies to be slow in taking down alt-right, hate content.
People forget, that things change. What if Zuckerberg decides that as a rich, white, male who is accused of indirectly helping Trump get elected, his future political prospects are better if he goes all in and casts his full support behind Trump? What if Twitter continues to have monetization problems and get bought out by a group of wealthy GOP donors?
How easy would it be to call any discussion of European colonialism and imperialism or of slavery in the United States, hate speech against whites? How easy would it be to label any discussion of increasing taxes because the 0.1% are not paying their fare share as hate speech against the rich. How about labeling any post advocating protest against ICE as targeted harassment?
If you knew that in 5 years, it would be the right that was running Facebook, Twitter, the ISPs, etc, what mores concerning free speech would you want to preserve, even when it involves a private entity.
I think a successful democracy in a polarized country involves both sides realizing that there will come a time when they will be out of power and encouraging cultural mores and norms that make sure they are able to communicate freely and have employment even when the other side is in power - either in government or in the private sector.