I'm with you, OP. Years of immunosupressive meds tends to make you slightly twitchy about dairy products left out for days, open jars of mayonnaise on the microwave, meat stashed in a saucepan on the hob, green slime that used to be pig based in the fridge and god only knows what gradually acquiring sentience in the slow cooker. I'd expect that pasta would then have been brought out to defrost, then left to sit, then microwaved, then left out again.
The OH used to get lots of stomach upsets, especially before he moved in. Not so many these days, as if he didn't want something thrown out, he wouldn't leave it on the counter/hob/in the oven/SC, would he?
The most spectacular event, however, was with an ex cocklodger of my acquaintance - I was in the process of throwing out unwrapped food of dubious provenance prior to going to the supermarket and he spotted me putting a tub of prawn cocktail in the bin. 'It only went out of date yesterday!' he cried. 'I'm not happy about it, it's shellfish'. 'Well, if you're too stupid to trust your nose, that's your loss' he said as he snatched it out of my hand, opened it and slurped everything in seconds, making a point of belching over me and saying 'Lovely' afterwards.
Less than an hour later, I turn to look at him in the Baked Goods aisle as he hadn't done his usual of hurling every cake in existence into the trolley.
He was bright red, puffing up visibly by the second and wheezing quite badly. One little diversion back to the Pharmacy section, three antihistamines, a few puffs of his inhaler and absolutely zero sympathy later, I'd worked out that it was the prawns being past their date and producing particular compounds that caused the reaction.
Hard cheese, I'm not worried by. Eggs are easy to test. Veggies are no problem. But things left out can be contaminated by flies, mice or bacterial/fungal growth and, if in the fridge for weeks, especially when poorly wrapped, can easily contaminate things I would believe to be safe. And if it's fish/shellfish or the like (or has already been opened), it doesn't get the benefit of the doubt.
If he doesn't want food to be wasted, he needs to put it in the fridge or freezer straight away. And buy/make less of it if portioning and freezing quickly isn't going to be bothered with.