Years ago, before browsers when the internet was still mostly usenet, there was a sudden flood of really gross and poor quality porn (just because it is an adult movie is no excuse for crappy film making) poured into wholly inappropriate newsgroups on usenet. There are specific areas of usenet for adult material but these pictures were being posted in placing like cooking groups, and the political groups.
The regular usenet readers asked the posters to confine their adult materials to the appropriate groups, and the porn posters came back with this lame claim that the first amendment gave them the right to post their porn in every single usenet news group.
I began to smell a huge rate here, and already having learned what the US government was like I started digging and sure enough the flood of porn was coming through various US Government and military sites. And sure enough, one month after the flood of porn showed up on usenet, Senator Exon introduced his amendment to the telecommunications act calling for government control and censorship of the internet, and making any obscenity on the internet a felony. Senator Exon took to the floor and showed his "Blue" book, a blue binder filled with the very images that had flooded usenet for the preceding weeks. And no sooner had the bill passed than the flood of porn ended as if a switch had been thrown.
So, if someone is flooding YouTube with porn, then it is an attempt to revive a call for government control of internet content. So, you need to ask, Que Bono. Who wants the internet brought under censorship.