The kid was "referred to" as a racist.
The “Socialist†label is usually meant, and commonly understood to mean, a person with strong liberal views. Not unlike calling conservatives “Nazis†and “Fascistsâ€.
The term “racist†used loosely against a conservative, is tantamount to the use of the "N" word by actual racists.
While not a “Terror cardâ€, “racist†and its close cousin “bigotâ€, are used by the left to “trump†an argument in which they find their own opinions challenged logically and effectively.