There are many everyday things we do to teach children that their body really does not belong to them even without realizing it. We show them this by example when we decide that we are going to hug them or kiss them, even if they do not want the affection. This indirectly teaches them they do not get to choose what happens to them and their bodies. It teaches them that their feelings do not matter, and that trusted people have the right to do what they want to them. While that may not be the message adults intend to send when they ignore a child's wishes, that is what the child can hear.
Some of the ways we can indirectly teach a child that they do not have a voice are:
Part of preventing child sexual abuse is changing that so that the child can have boundaries, can say "no" when someone does something that makes them uncomfortable. This is not taught so that a child can learn to say "no" if someone tries to sexually abuse them. It is taught so that the child can be more confident in who they are. It is a fact that, consciously or not, abusers tend to single out children who seem timid, lack confidence, or come from a broken home. Abusers can sometimes single out children with disabilities, physical or mental. Abuse is a process that happens over weeks, months, and even years. The abuser or potential abuser will work to put the child in a spot where if they do something sexual to the child, the child will not mind, as well as working to overcome their own objections to abusive behavior.
By teaching a child from early on that their bodies are theirs, and they get to choose what happens to their bodies, we can give children the confidence to make an abuser or potential abuser gloss over that one child. Or, we give our children the ability to tell us when they are uncomfortable around someone... long before abuse happens. And then, we can review the warning behaviors and have a conversation with that person, and they can get help.
In many areas, we must teach children that their body is theirs, and they have a right to their body, their feelings, and themselves.