That's actually not true, and I think we've had this discussion before but I'll say it again: by all evidence of developmental science, when children are left alone to figure things out for themselves, they do develop bad attitudes and emerge as bullying and prejudiced adults.
You have to teach a child what it means to be a good person, otherwise they won't be one.
You have it the wrong way round: good people don't grow on trees; it's shitty people who emerge organically.