There is no weapon the Left loves to use quite as much as the ad hominem. And the less true a charge a liberal makes against a conservative is, the more loudly and indignantly it will be shouted.
Support traditional marriage, and you're a "homophobe." Support the enforcement of the law, and you're a "fascist" (these days Rahm Emanuel and the other enemies of free speech among the legions of political correctness have a far better claim to that label).
And be a conservative of any kind, and you're automatically a "racist."
Peter Berkowicz herein examines that last libel in particular.
HT: Real Clear Politics