My daughter did a huge science competition earlier this year that involved foodborne illnesses and food safety, and I coached her. So here's what the Centers for Disease Control taught us: TWO hours (not four, as someone else posted) is the outer limit for food sitting outside the fridge. After that it's starting to cook up bacteria. That turkey sat out for 11 hours. I would never eat it and wouldn't let my family eat it either.
And pizza? Heck no, that goes in the fridge too. Look at it this way -- you would not eat lasagna that sat out on the counter all night, right? So why do your friends think pizza is different? Pasta (crust), cheeses, sauce, etc. in both of them, so why would one be immune to bacteria and the other not? Pizza is not some special exception to the rule of refrigeration and it's some kind of urban myth that it doesn't need refrigeration. I bet the folks who eat it after it's been out haven't mentioned that they have some interesting stomach rumbles and trips to the toilet after eating it; they just haven't thought to connect the dots. It's just dumb luck that they haven't gotten something worse.
I know how you feel about your in-laws and things like leaving the chicken-veg dish "under the window unit." My sister-in-law and her husband used to live in a tiny apartment in Europe with a tiny fridge (that they never even bothered to plug in) and bought food in smallish amounts every day to cook and eat that night. They just let any leftovers sit out to be reused for lunch the next day or dinner the next night, if there were any. And for years my brother-in-law complained of his delicate stomach and digestive problems! They are bright, well-educated people who did not think to relate his always delicate stomach to the fact that they frequently ate food that had sat out all night and half the next day. They were used to homes with tiny fridges and a culture where many folks shop almost daily and don't bring home giant grocery loads to stock in a fridge, but I can't believe they didn't understand that leaving food out like that was nuts. Finally they moved to a larger place (still with a tiny fridge) but actually plugged in this one and started using it as if it were a revelation. My brother-in-law's stomach issues improved....!