My Mother told me about the first time I as a little tot, saw a man with only one leg. She said I gazed at him in some amazement but said nothing. I don't think the experience was particularly traumatising... Of course if my Mother had reacted with horror, shock and surprise at seeing a man with one leg, then I would no doubt have realised something was wrong and become distressed and upset myself. And of course having learned from this, continued in future to find the sight of people with missing limbs disturbing and upsetting. Parents need to be very careful about how they react to things in front of their small children. Phobias, hatreds and predjudices of all kinds, can be learned from parental behavioural cues, very early on. That's one of the reasons it's so useful to have minorities appearing in safe normal contexts in media such as childrens telly, so that they learn early on that these are not strange alien creatures to be hated or feared, when they become adults.