I was going to say "an animal that would eat the stupid" because we have so many of them in America. Stupids, I mean, not stupid-eating animals. Ideally this predator would be able to smell stupidity and home in on it, preferring fools and morons to all other meals.
Since it has to be based on real animals, I guess I'll have to compromise. I would start with a large predator -- tiger, grizzly bear, something like that -- and infuse enough chimpanzee brain to increase its intelligence without sacrificing killer instinct. Bonus points if I can increase the functionality of its paws to make them more like hands while maintaining the killing strength of its claws.
I was going to say "chameleon skin" but the loss of fur would likely make it unable to survive in colder areas. I want a beast that can threaten fools wherever they go.
Introduced en masse, it would tend to feed on the stupid, since they are by nature unobservant, have little to no grasp of concepts like safety or mortality, and are slow to come to decisions, even really important ones like I WILL RUN AWAY NOW.