That's first-order ethics. Some of us have second-order ethics. The philosophical introduction to this is Smilansky's designer ethics. The wording is fairly odious, but the concept is simple: e.g. Heidegger was a Nazi, and that means that his opinions are suspect even if competently phrased and argued. A common example of this is discounting scientific claims put forth by creationists, intelligent-design proponents, and other apologists; they are arguing with a bias and it is fair to examine that bias.