Oddly and disappointing enough, I find the appearance of my helmet plays a SIGNIFICANT role in how people react to me.
When I first starting bicycling to school in 2007, I wore an old helmet from the mid-90's round design. The number of harassment wasn't much but still some bad interaction with motorists were there.

Once I switch to a Bell Sweep, I was mistaken as a cop for SIX TIMES within a year, and ZERO bad interaction with motorist...