I’m against sauces on good burgers. You want mustard? Fine. Relish? Fine. Mayonnaise? Fine. Heck, I don’t even object to others putting catsup on a burger, although I’d never do such a thing myself.
That said, I have no intention of, nor any interest in, trying to make you like anything. As to what your mother might wish to do, well, that would be between you and your mother.