I disagree. The idea behind sites like gab is that sites like Twitter are increasingly functioning like public spaces, but they exercise great ideological contr

I disagree. The idea behind sites like gab is that sites like Twitter are increasingly functioning like public spaces, but they exercise great ideological control over what one is allowed to say within those spaces. The folks behind gab and similar sites think that one should not be banned from Twitter -- that is quite different from speech without consequence. One can still be humiliated, shamed, and socially shunned in every way possible. You could still be fired from your job. You could also just be completely ignored -- merely not being banned from Twitter does not grant you even a single follower. To illustrate the issue, consider that one can be suspended or even banned from Twitter simply for stating (rightly or wrongly) that there are two genders. But Sarah Jeong-style tweets are considered perfectly fine, even though they are hateful and racist in many ways. I think these examples illustrate that what is at stake here is much more than just the ability of mass murderers to spew hatred. To make your analogy stronger, you would have to imagine a world in which theaters had become the standard place to talk and engage in discourse amongst tens of millions of people simultaneously.