When anyone criticizes the president, they are labeled as a racist?

Because traditionally, calling someone a "racist" has been an argument ender, a checkmate. "You're a racist, therefore your argument is invalid." The militant left think if they work this little trick, they can deflect any criticism of their Messiah. But what aggravates me the most is that people spend time trying to debate that logic instead of telling of these people to STFU.