Liberals are incapable of addressing a real argument hence their standard tactic of resorting to ad hominem attacks.
Last time I debated with a liberal I was able to provide facts that even she didn't dispute...so she just said I was narrow minded...for sticking to reality. Facts and truth didn't matter to her and they don't matter to liberals/progressives. It's why they embraced a candidate with no experience and no real ideas who simply espoused "change" without an substance.
I just got finished with the “5000 Year Leap”, and I thought it was absolutely fantastic. Should be required reading for ALL high school students. A precise and accurate summation of the philosophy behind the “American Idea” (which is probably why the left hates it and its author).