That's where the joking about it comes from; ketchup on hot dogs is one of those things that people take jestingly serious with tongue firmly planted in cheek at all times. Nobody actually cares, nobody's actually going to kill you in Chicago despite my joke, but people interpret the joshing as caring and demeaning because nobody can actually take a joke any more, as evidenced by GP (and which is far more often the problem). And yet here we are, lamenting the downfall of society.
I can't even fathom a world where someone giving a friend crap over lunch for their choice of condiment is enough to start a Serious Conversation about Culture. That's funny in itself, honestly, but I don't want to live in that world. That's why I eschew social media altogether.
I remember when I was a boy, laughing was something to be celebrated, because sharing something funny with your friends was one of the high points of life. Actually cutting loose and laughing with your friends about the stupidest things is easily one of the best feelings you can experience, but now every time I genuinely laugh at something that I find funny, I often have to look around and be worried about who saw me do it. It's genuinely depressing, the older I get. I don't even have humor any more. Now I just have liquor.