Never have I heard that slaughter is the only viable option. Never.
Slaughter or starvation? Why are those the only two options spoke of when there are many other ways to end life? I've had to let horses go, so have many friends. Not one was shipped or starved.
I couldn't imagine sending an old friend "who served me well" off on any journey without me being there. I'll return the favor & serve them well too (& not with a side dish).
Let me start this by saying that any of my horses that needed it have been euthanized and buried here.
When you come here, to this site, you are preaching to the choir. The people here are the ones who care about their horses. When we talk about slaughter or starvation we are talking about the multitudes of people who, unfortunately, exist.
Just because we don't own those horses do we not care about them? Do we turn our backs and pretend they don't exist? There are tons of people who treat their horses as objects, and as soon as that object loses its usefulness, it gets sold or disposed of. They don't care where the horse goes, as long as it doesn't cost them anything. If I had the money I'd go buy all those thousands of horses. WE care about our horses AND we care about the horses owned by those who don't, care.
Save your judgement for the people who don't care, those who leave the horses in a pasture (with no grass or water) to starve, to those who send old crippled horses to auction, knowing exactly where that horse will end up, and don't care.
We either have slaughter houses in the USA, that can be monitored, or we allow horses to be transported to other countries to die horrifically. Those are the choices. I would love to live in your perfect world, where dogs and cats all had wonderful homes also. But, we live in this world.