In the end we are purists. Pure to our own tastes. Do I put ketchup on a hotdog? Sure but I also eat them with relish, onions and chili. Come to think of it isn’t chili a derivitive of a tomato, pretty much where ketchup comes from.
I also eat corned beef and cabbage, sometimes with vinegar and sometimes with butter on the vegetables. I eat french fries sometimes with ketchup and sometimes with malt vinegar. Pork chop sandwiches sometimes with mayo and fried onions and sometimes with mustard.
You get the idea. There is one rule that I will never, ever break: Pastrami and corned beef sandwichs must be served with mustard. That’s just me.