The theory of evolution has been uniquely politicized, and thus "critical examination" raises red flags in a way that "critical examination" of, say, the theory of relativity doesn't.
To draw an analogy, the Theory of Evolution and the Theory of Relativity are both well-established scientific explanations, just as the Second Amendment and the Third Amendment are both well-established articles of the Bill of Rights. In each case, people are much touchier about the former than the latter, because the former is under sustained political attack while the latter is questioned only by an insignificant fringe of cranks.