Bruce Jenner -- Kim Kardashian's Flour Bomber Is an 'ASS'

Bruce Jenner is rallying behind his stepdaughter Kim Kardashian -- claiming the rogue PETA member who dumped flour on her last week is nothing more than a pathetic little "ass."

Bruce and Kris Jenner were leaving LAX yesterday -- when a photog asked what they thought about the flour-bombing PETA activist Christina Cho blasting Kim for wearing the flesh of dead animals.

Bruce didn't miss a beat, calling Cho an "ass." Meanwhile, Kris played coy.