So, the parents objected, you got cautioned and then you post a picture of their child on a public forum? I don't think this is responsible photography at all sorry.
If anyone objected to me taking a picture of their child, I would immediately delete it. I assume you were in a public place and what you were doing was legal, but if a parent objects, surely common decency would prevail?
Or yknow rather than go whine to the police the parents could have had the decency to come up to him and ask him politley not to take photos of their daughter?
It's sad, but the society we live in makes us suspicious of everyone.