“The films showing sanitation workers cleaning up show bags of dead chickens piled high and some exploding as the garbage truck mashes them down.”
This is simply not true. There are no such films. These are bags of ordinary garbage, including some dead chickens.
There may be some small operations that can’t find anyone to process the few chickens they have, so they have to throw them out, but it is absolutely not the normal case. All the big operations have people working all night erev yomtov and all day motzei yomtov cleaning and kashering as many chickens as they can, so they won’t have to be thrown out when the 72-hour deadline comes.
Even if they were thrown out, though, I don’t see how that is anyone’s business, or why anyone would have a problem with it. Let’s suppose that the cost of processing the chickens in time is greater than their value; in that case it would make sense to throw them out. It would in fact be bal tashchis to spend so much money to salvage them that with the same money you could buy more fresh chickens when you need them. Usually that’s not the situation, but if for some reason it is then throwing them out would be the right thing to do.