Nasty, but I still think you should have raised pre-flop; if the BB is overly aggressive then that plays into your favour. Maybe he re-raises or pushes all-in, the pocket 4's might fold and you should be feeling good going up against the BB with your K's.
Of course in reality, the guy with the 4's would have called the BB's all-in and won a bigger pot because it seems as if no one on PP (and it may be the case on other places, I play exclusively at PP so I notice a lot) wants to release a pocket pair until they at least see a flop.
