You wouldn't want to engage in such exposure without the individual in question being under the care of a therapist, though, would you? It's not just "make them face their fears continuously and without support"; it's a process.
I haven't worked in therapy professionally, but I've got a lot of personal experience dealing with traumatized individuals (some in therapy, some not; I always recommend therapy, but a lot of people don't have that option) -- and I do know that throwing people in the deep end of the pool rarely works well.
The fact that I'm not a therapist is exactly why I'm not qualified to subject my users to exposure therapy -- especially without their consent.
Also, regarding "some are not ready but they should not be on the internet at all." -- the internet is not a monoculture, and has not been for decades. There is plenty of room for spaces with varying levels of supportiveness.
TC is a supportive safe space. That involves keeping out those who cannot behave supportively or at least neutrally.
On the internet, everyone knows you're a cat — and that's totally okay.