as a parent, first, do no harm.
A parent that abuses their child will often have the child taken from them by a child protection agency. A parent that pushes their child toward surgical reassignment of sex is abusing their child in the extreme.
A young child CAN NOT give informed consent due to immaturity. Many whom have undergone this procedure regret in greatly when they grew older. They are victims of their parents actions. Once they are 18 they can give informed consent and do any damn thing they want with their body.
Child abuse is illegal. This is child abuse.