That second point would require intimate knowledge about which animal parts would be disposed of if they didn’t find a buyer.
In reality, everything is used. If there wasn’t a market for part of an animal, a use was found and a market created (which is part of the reason why industrially produced white sugar, beer, wine, apple juice, potato chips and bread usually aren’t vegan).
Anyway, vegans usually don’t care about whether an animal product could be leftover. Their philosophy boils down to “Just fucking leave animals in peace.”
Their philosophy boils down to “Just fucking leave animals in peace.”
It’s more complicated than that unless you don’t understand how many animals die when you clear farmland. Every crop you eat came at a cost to animals, if there’s no amount you deem acceptable or unavoidable your only option is to exclusively eat food you grew yourself, and that still alters the environment to be less favorable to animals, you just don’t directly kill them like large scale farms do.
There’s also the pesky detail that if minerals in the soil are taken up into plants, and plants are then eaten by animals, then animals need to go back into the soil we grow our crops in or the the soils get depleted of minerals. That’s why most salt is iodized, because we’ve leached all the iodine out of our croplands and never put it back. There is only so much fossil fertilizer in the world. Eventually we are going to have to accept that we are part of nature instead of separate beings above it and doing things to it. Factory farming sucks and needs to end, but we can’t “Just fucking leave animals in peace.” we are not separate from them. They are us and we are them.
