When I was younger, as in 5 or 6, I had to wear sunglasses all the time because my eyes were messed up and very sensitive (I don't remember exactly what it was), and my aunt has that problem also. So, it doesn't ever bother me when I see someone wearing sunglasses in a seemingly inappropriate situation. Besides, it made me look like a complete balla.
And even if he is just wearing it as an accessory, it's not really any weirder than, say, those Fidel Castro-esque hats I've seen some women wearing. Fashion is bizarre, just accept it.