'Pick the Target, Freeze It, Personalize It and Polarize It.' - Saul Alinsky, Rules for Radicals.
They honestly can't help themselves; they've been conditioned to respond this way.
Erratic and emotional is pretty much the rule for Democrats. That's why they are democrats. They make good actors and entertainers because they pretend to live in a fantasy world every day. What they don't make is good engineers or people who otherwise construct useful things for the benefit of mankind.
I have long remarked how conservatives tend to deal in tangibles, and Liberals tend to deal in non-tangibles. If a conservative produces Crops, or Oil, or Buildings or whatever, Liberals produce "education" or "entertainment" or "legal services" or "news." No actual tangible work product.
That's not to say this is always the case, but I have noted that people such as Lawyers, Entertainers, News Broadcasters, etc. tend to be Liberal, while Doctors, Engineers, Manufacturers, etc. tend to be conservative. I have always thought people who are geared toward the abstract and emotional pursue such careers as are dominated by Liberals. It has been mentioned more than once that Theoretical Physicists tend to be Liberal, and Experimental Physicists tend to be Conservative.