>I just fail to see how quantity factors into anything here.
Because you can overload any online discussion / sphere with that. There were so many that X effectively banned searching for her at all because if you did, you where overwhelmed by very extreme fake porn. Everybody can do it with very low entry barrier, it looks very believable, and it can be generated in high quantities.
We shouldn't have clamped down on photoshop, but realisticly two things would be nice in your theoretical case, usage restrictions and public information building. There was no clear cut point where photoshop was so mighty you couldn't trust any picture online. There were skills to be learned and people could identify the trickery, and it was on a very small scale and gradual. And the photo trickery was around for ages, even Stalin did it.
But creating photorealistic fakes in an automated fashion is completely new.