This isn't a fully-general argument for censorship of any given subject that provokes disgust; it's quite specific to violent pornography.

I didn't notice this on the first read-through, but cupholder's comment brought this to my attention - the actual content seems to be an irrelevant factor in your general principle, especially the 'pornography' part. Surely we could say the same thing about non-pornographic violent media. Furthermore, if reading the Oxford English Dictionary or looking at Starry Night increases violent tendencies in the same way, then your argument works just as well.