?Seinfeld? alum Jason Alexander found himself devoting part of his week to fending off criticism, after commenting on the fact that newly tapped national security adviser Lt. Gen. H.R. McMaster once apparently referenced Alexander?s ?Seinfeld? character George Costanza. The heated back-and-forth began Monday, when it was pointed out to Alexander on Twitter that McMaster once apparently referred to targeting enemies with bombing as the military equivalent of ?George Costanza in ?Seinfeld,? ?leave on an up note? ? just go in, do a lot of damage, and leave.?