The argument in favor of absolute free speech for me was basically “let everyone hear everything and make up their own mind”. This presumes that people are swayed by the content of an argument. This is a false assumption, people are mostly swayed by the volume of the argument. This is well documented in psychological research. Now, if everyone had the same level of visibility for their personal speech this would just lead to an ersatz version of opinion democracy, where the most often held opinions would rise to the top, which wouldn’t be a bad thing.
But people don’t have equal visibility. The reach of a wealthy or famous person is so much greater that in the political arena basically only the speech of the wealthy and famous ends up having enough volume to convince people, even if it starts out wildly unpopular and even if it is objectively false. Social media are especially sensitive to this thanks to the ability to buy access to views without the viewers even realizing, to micro-target audiences, and to have zero independent vetting of what is said. This then perverts absolute free speech into a weapon used by the powerful to deceive and subvert democracies.
That’s why I think that to protect democracies we must have some limits on the ability to get speech amplification through (social) media, but I don’t have a hard and fast rule for what that should look like. It is far easier to say “let everything pass” but that is the easy way out and ultimately bad.