It’s not exactly breaking news that Donald Trump can be petty. That he can be needlessly vindictive. That he can sound like a kid in fifth grade when he puts down opponents with dopey, demeaning names like Crazy Bernie (Sanders) and Jeff Flakey and Psycho Joe (Scarborough) and Little Rocket Man. But I have to admit to a guilty pleasure: When he calls Elizabeth Warren Pocahontas, I laugh. Out loud.