The issue most people would have with seeing the sausage being made isn't necessarily watching the slaughtering process but with seeing pieces of the animal used for food that they would not want to eat.
The analogy here would be watching a live cow get slaughtered and then butchered from scratch in front of you, which I think most Western audiences (more than a few) might not like.
I am asserting that you could do all of that in front of a random assortment of modern Americans, and then cut steaks off of it and grill them and serve them to half of the crowd, and most of those people would not have an problem eating those steaks.
Then if you were to scoop up all the leftover, non-steak bits from the ground with shovels, throw it all into a giant meat grinder and then take the intestines from a pig, remove the feces from them and fill them with the output of the grinder, cook that and serve it to the other half of the crowd, then a statistically larger proportion of that crowd would not want to eat that compared to the ones who ate the steak.
Some things just tickle the brain in a bad way. I've killed plenty of fish myself, but I still wouldn't want to eat one that's still moving in my mouth, not because of ickiness or whatever, but just because the concept is unappealing. I don't think this is anywhere near as binary as you make it seem, really.
Imagine that to cook that pork chop, the chef starts by butchering a live pig. Also imagine that he does that in view of everyone in the restaurant rather than in the "backyard" kitchen let alone a separate butchering facility hundreds of miles away.
That's the sushi chef butchering and serving a live fish he grabbed from the tank behind him.
When you can actually see where your food is coming from and what "food" truly even is, that gives you a better grasp on reality and life.
It's also the true meaning behind the often used joke that goes: "You don't want to see how sausages are made."