The difference is one (R rated movies) is something social standards classify as 'normal', and people don't want to be overly critical of 'normal' since that would imply being critical of the status quo and oneself. The second (scat and other fucked up shit), is viewed for pleasure only by a tiny fraction of the population. Since most people have an attraction to the obsene and violent, but are ashamed of it, they can classify that tiny fraction of the population which holds a stronger, more deliberate and unashamed position as being the alien other, and therefore, evil and unworthy of our empathy. By attacking the ones who are different, society bonds and enforces the weak links that tie it together.
It's very stupid indeed. If they don't like it don't fucking watch it. All that you say is very true. Some people aren't stimulated and wired like the rest. Same way some people get hardon for balloons popping or girls with red streaks in their hair. To each their own...
I think the video is hilarious and watching people make reaction videos is very rewarding, atleast to me and b4. Even my favorite comedian made a reaction video, if I ever meet him I will be able to tell him "You remember that video you had a reaction to? It was me

". Imagine being the person that mindfucked another person without even doing harm to them or anyone else. You just did something so unexpected and bizarre yet legal that it will stay with them for the rest of their lives.
When they're old they're going to tell their children, "I watched this video called 2girls1cup and it was so fucked up. Nothing like the ones today". If they've seen Cakefarts next time they eat a cake they will think of that girl, "You know what I like the most? Cake farts!" and picture her farting on it. Same goes for PuddingFarts, Chocoteeth, etc...
I dunno about you guys but it's very stimulating to think about that. I don't really care if they don't know who we are. I'm not in it for the fame, I'm in it for the LULZ. Are we really the fucked up ones? We set the dominos, you guys are the ones that tip it over. The fucked up ones are the people who watch the ENTIRE thing, secretly enjoy it then ridicule it, fucking hypocrites. 2girl1cup, cakefarts, etc has tens of millions of hits combined so it comes to show how curious people really are.
I'm not taking credit for making the videos, but we are the ones that blew them up. Once people start copycating I just drop it. Same for all my memes, I just like setting the dominos. 2Girls1Cup wasn't illegal. Where Ira went wrong was filming beastiality. Unlike the girls who did Cakefarts knowingly, animals can't reason. It's kind of in the same category as CP and that's definitely punishable. I do wish him luck though as he changed the shock game.
Again b4 was the mastermind behind everything, we just had a mutual bond and started working on them together.