Butter (or spread, but NOT margerine, yuck)...
Is required on toast and bread if you want to put a sweet, syrup based topping/filling on there.
This is because the osmotic action of the sugar syrup draws moisture out of the unprotected bread, causing it to dry out, and changing the texture to a rather unpleasant crispy dry sorta thing. Yuck.
Butter/spread is required with other fillings to prevent the bread going soggy, for example, cheese and tomato sandwich without butter will result in a soggy mess where the unprotected bread absorbs the tomato juices.
Acceptable non-use of butter./spread is...
Using a thick layer of cream cheese, peanut butter, or nutella.
So yeah, he's right, and you are extremely weird, aberrant and WRONG and VVVVVU.. (but in reality, you do you and all that :D )