I know that when I'm driving a car, I specifically behave differently when I see a bicyclist with a helmet vs without. /s
This just sounds so preposterous. First off, I doubt the average driver notices bicyclists at all. Of those that do, I'd seriously doubt if they even consider that they are wearing a helmet or not and just express frustration at the bicycle being there in the first place. The suggestion that a driver notices a helmet and acts more aggressively towards the rider or that they give a wider berth to the rider when not wearing a helmet is just "trying too hard" for lack of better words to describe my incredulity.