I find that very odd advice. The child (teenager) would be spying/peering on you. You have a right to be as you want to be as long as you have a fence (or whatever) that protects you from using your yard naturally. If they use a trampoline, or climb a tree that allows them to see into your yard then they are at fault, not you. Don't worry about it but do use sunscreen. P.S. Masturbating or fucking in your backyard probably is not using your yard "naturally" (no matter how desirable) but that is open to debate.