Some interesting responses in this thread. 18 of them. I don't know if I can reply to all of them or even many.
Cybersex IS speech, and porn is art (however far from fine art it is).
What's the reasoning behind this? Cybersex is people typing words, but that doesn't make it speech for the purposes of free speech. Neither is there any reason to support that porn is "art." Porn is a product like a Big Mac, except instead of sugared bread and soya-meat there's dongs.
When you consider how very central sexuality and control of sexuality has been to the political process across the globe, it doesn't make any sense to attempt to cast them as otherwise.
The thing about free speech is, we don't need proof it leads to a better way of life.
Here's more assumptions with no logic behind them.
Control of sexuality and free speech are both contingent upon their effects, like all other policy choices.
If you're going to make a deontological argument, you're going to have to argue for some moral superiority of these things, which in an atheistic pluralism has no inherency.
That leaves you with arguing for their utility, and I await your doing that.