this seems like a fairly weak criticism. it would be better to have more comprehensive description of methods, but even if they did directly ask "is political correctness a problem in America?" I don't think that invalidates the findings. most people know what the term means.
and given that the term has a negative connotation built in (for the majority of people) it actually _is_ doing a good job of revealing cultural divergence with progressive activists, who are the only group that does not hold that connotation.