The words used to stigmatize a person or a food are always associated with YUK language. For the very young or unsophistocated words like "nasty" ,"filthy", "dirty" or simply "YUK" conveys enough disgust to teach us to reject AUTOMATICALLY any person or thing thus described.
Older and wiserwe use words like "contaminate", "poison", "adulterate","pollute", to proscribe by generating a sense of revulsion.
All these terms discourage the hearer from thinking about WHY.
Why? why is something dangerous, nasty, evil? To label a thing or a person by first tainting its existence makes all further descriptions of it fall under disrepute---even if the actual factors involved are neutral or even comparable to accepted standards.
We cast things, customs, people in this manner until we feel guilty if we even give them a fair trial. If we even say "hold on for a minute--let's think about this---" TO OURSELVES, we feel separated from whatever community we are a part of.
The film "To Kill a Mockingbird" was of course the dramatization of what occurs when a man attempt to give a fair defense of a black man in a southern U.S. town in the 1930-40s. Trying to get people to THINK past their conditioning was the challenge.
The yuk factor trumps fair reasoning for lots of people.