I've noticed a pattern in movies, characters with round dark glasses
are usually portrayed as pure evil or bad. I'm not talking about those light purple round glasses that hippies have or the untinted ones that old-timey doctors wore, Im saying 'so dark you cant see through them' glasses.
Anyone whos seen 'O Brother Where Art Thou' should know what im talking about, hell the villian's defineing characteristic throughout most of the movie is those glasses, and you know hes not coming back when you see those glasses washing away in the flood.
I haven't just seen this recently either. The oldest example I know of is from '67 in 'Wait Until Dark' Alan Arkin's character is a killer and you know this from the first scene he's introduced. However charismatic he is throughout the movie, you are still know he is bad because of that first impression, with those round dark glasses. This is also in 'Natural Born Killers' with Mickey Knox. It seems when he isn't wearing those glasses he is more rash and emotional, but when he has them on he is steady, calm, almost souless.
Personally I believe that movie directors do this because with the round glasses it looks like you have eyes that are just holes.
and after all... "The eyes are the mirrors of the soul"