He’s crazy as a bat

You can guess who the speaker was referring to.  This is a nice congruent conflation of “crazy as a bedbug (or loon)” and “batshit crazy”, both describing someone who is insane.  “Bats in the belfry” also come to mind, although that is an old-fashioned phrase.  “Crazy like a fox” (clever) might have been in the mix, but I doubt it based on the person the speaker was referring to.  Hint:  he denigrates war heroes, and even when they’re dead.