There is always possible indirect harm for the fact you are selling a baby chicken. People think they are nice and cute whether colored or not. Should we outlaw the selling of natural different colored fuzzy chickens as well?
You know full well that would be impracticable but you also see that selling little teletubbies is more likely to lead to poor treatment of the chicks when they grow up - or sooner if the kids get bored quickly and the parents decide they don't want the hassle.