Children should not be talked about sex in the way the article describes.
But children at about 3-4 years of age should learn the appropriate names for private bodyparts and the difference between good touch and bad touch and good secrets and bad secrets, and in what scenarios someone is allowed to touch your private parts, as well who to tell if someone touches you in an uncomfortable manner.
Parents do not do this type of education, and its not a good thing to avoid this discussion.