What do I do when my manager puts himself down in front of me? He does a lot, like he’s angling for some reaction.
This is a classic double-bind. If you agree, you’re essentially saying he’s an idiot. If you disagree, that’s insubordination. I’d deflect the remark with some clever non-sequitur like “Did you know cats can vomit at will?” and wait a beat. Then look away and say, “So, about the project plan…”
OK, maybe that’s not the way I’d actually handle it. I’d watch the guy carefully, though, and see if he’s really playing hardball. That means, he’s putting himself down in order to set you up, lay a trap, so that he can take out his self-loathing on a defenseless target. This could be a woman, too, in fact the classic gambit is “Do you think this dress makes me look fat?”
Sometimes you can talk your way out of it.