Pineapple pizza haters are, for the most part, pseudo food snobs.
It's all in the execution.
If you're eating a soggy pie, obviously you're not going to enjoy a wet wedge of pineapple on it.
Prosciutto pairs well with melon and that's generally well accepted. I don't see pineapple with parma ham on a pizza as too much of a stretch.
So long as it's properly grilled and not wetting the pizza, it's fine. Same with courgette or aubergine slices.
There are also people who'll scream bloody murder over creme fraiche on pizza, when it's actually delicious. Traditionally, it's used in flammkuchen (tarte flambée), which is almost a pizza, except that it's incredibly thin and it's dough is made out of only water, flour and some salt (though some recipes call for some oil). At any rate, creme fraiche with onions and lardons or smoked salmon is amazing.
And pineapple on pizza is a-ok. Magnus Nilsson and his two Michelin stars clearly don't have a problem with it.
My guess is the people who absolutely hate it have a biological predisposition against it, like the people who can't stand coriander.