It's wrong in class terms. Pizza's are proleterian food - good and cheap and filling. Pineapples were a complete luxury - to the extent that when they first came to Europe they were displayed rather than eaten, and you can still find gates of mansions topped with stone pineapples because they indicated luxury. So it's wrong because it's a class war on a plate, and that's exactly what it tastes like.
That some toppings on a pizza aren't available to all (even historically), does not mean that others must not enjoy those toppings. One person having pineapple on their pizza does not make pizzas unavailable to the proletariat.
Class war is nice. Pizza could be a symbol for justice and revolution!