The argument is that if kids are taught about sex and told that some people like to shove pineapples up their butts, they will become sexual deviants
That may be your strawman argument. but it isn't even close to what I've been saying.
What I've been saying is that given the typical sexual role models of modern youth (basically none) porn will fill the gap and teach them porn-sex is normal-sex. Furthermore, that a "5 second" conversation, or even even a few substantial conversations, isn't enough to fully overcome those learned attitudes about sex.
Citing your 3-year old's statement that she isn't a dinosaur as proof of a child's ability to understand something for which they have practically no other context is ridiculous. If children really were so rational then it would be fine to let minors enter into legally binding contracts and age of consent laws would be completely without merit.