The most obvious negative reaction Ive had was when I was talking to the girlfriend of a friend of mine in a pub last year. Shes of middle eastern extraction, my friend is a white guy, who himself has had a shaved head in the past. So, I was talking to her and my friend turns up and tells me to take my hat off (I often wear a flat cap). I did so and she never said a word to me for the rest of the evening. For the record, I am absolutely not racist or right wing or anything like that, and it came as something of a shock to me. Still dont understand it to this day and havent seen my friend since so I dont have an explanation, but I no longer expect one.