It's a thing, I have a friend that is afraid of any white condiment, I don't have a fear of condiments but too much of a condiment makes me uncomfortable.
Ok, I get it - mustard is not the condiment of choice for a lot of people.
Many find yellow mustard to be disgusting and even smell horrible. For me, I love it on nearly everything - including my scrambled eggs (you should try it sometime).
Never, though, would I ever chug mustard.