Why is Trump so obsessed with bodily fluids?

Clinton’s bathroom break — or, more precisely, Trump’s revulsion toward it — lies at the intersection of his misogyny and his fastidiousness. He’s a germophobe who once labeled himself “a clean hands freak,” called handshakes a “terrible custom” and said that the obligation to engage in them was one of the great curses of celebrity like his.

Even so, a kidney doctor I know was baffled by his latest outburst.

“Urine is sterile,” Maya Rao, an assistant professor of nephrology at Columbia University, pointed out. “It’s not ‘disgusting.’ Wow. I literally feel like I’m dealing with an elementary-school child and we’re talking about cooties.”

Trump is routinely — and rightly — tagged as a playground bully, but that phrase doesn’t do full justice to his arrested development, his potty mouth and the puerile nature of his vulgar bleats.