This is worth a couple of minutes of your time. Progressives have lost (if they ever had them) three capacities: (1) to engage in careful analysis of difficult and important concepts; (2) to follow complex arguments; and (3) to argue, in the sense of persuading, rationally, those with whom they disagree. The reason for these incapacities, I think, is that progressives are dogmatic. They believe that their beliefs are unquestionably true and that their values are unassailable. If you believe that you are on the side of the angels, why bother analyzing, understanding, or arguing? Anyone who disagrees with you is, by that very fact, either stupid (i.e., unintelligent), ignorant (i.e., uninformed), or bigoted (i.e., malevolent).
As for why progressives are like this, look no further than the domination of academia by leftists. Some progressives have never encountered a living, breathing conservative. Their conception of conservatives is, as a result, cartoonish. I know whereof I speak, because I used to be a progressive. I vividly recall telling my fellow progressives that the only real debate is between liberals and progressives. Conservatives, I said, should be treated like cockroaches and stepped on. Having been both a progressive and a conservative, I can attest that, on average, the latter are far better at analyzing concepts, understanding other people's arguments, and arguing.
