Doesn't matter if people want to go there. The point is that it exists, and the model is governed by the taxpayers.
Impact of a government social media: If you get banned from Facebook, you have the option to post your non-illegal content on townsquare.us. Therefore, your free speech rights are not being impacted. The right to speak is not the right to be heard by the audience of your choice.
I get that you don't share concerns about deplatforming, but presenting this as a solution to those concerns is not accurate.
But none of those platforms draw a direct line between the constitutional guarantee of free speech and implementation of that speech. That’s the idea behind the public option: it’s the constitution with teeth, freedom in its purest form, while leaving corporations open to experiment with restrictions as the market demands.