It looks like correct usage to me:

https://www.wordnik.com/words/idiot

The hypothetical person is certainly not offended, and previous usage as a medical diagnosis is considered archaic.

Yes?

No.

I'm also not really sure why apples were singled out here, since they're an example of produce that does last pretty well without refrigeration.

It was an actual incident that I witnessed. Perhaps it stuck with me precisely because apples keep relatively well. But there they were, going bad.

If you aren't homeless, no one expects you to sit and eat a giant bag of apples all by yourself within one to three days. People in housing who are gifted a large amount of produce or whose gardens overflow will post questions to forums concerning creative uses. They will can, pickle, etc the excess -- the amount they can't reasonably eat fresh. People expect you to eat an apple or two in a day, not twenty or thirty of them. Unless you are homeless, I guess. Then suddenly you should be grateful for 30 apples instead of revolted at the idea of trying to finish them by yourself before they rot in the heat.

Canning, pickling etc is beyond the means of a homeless person. So I have no idea why any middle class person would think giving a huge bag of a single type of fruit to a homeless individual in hot weather would make any sense whatsoever. I cannot fathom it.

If you give a big enough bag of even a hardy fruit to someone with no means to preserve it, it will rot. Even apples.