I have left strict instructions for myself to be shot, Bruce. I have no intention of being patronised to death by do-gooders or being a burden to the taxpayer. I don't know if my organs are going to be usable (I'm on the organ donor list and have inquired about the possibility of making a live donation if it's possible), so, if not, my remains are to be sliced 'n' diced by medical students or shoved onto a body farm for forensics trainees to admire its gooey decomposition. Either way, I ain't hanging about. My conscience - whatever that is - tells me that it's entirely wrong for people to suffer what is often a very painful and debilitating demise, believing they're a useless burden to their families, if they have a functioning brain to think with. You have a problem with any of that, that's your view, not mine.
As for the horsebox issue: you're quite right that horses don't know the time of day. That's why they're not trusted to drive themselves to racecourses. They'd have no sense of when the first race was due off. So humans are employed to do that, and that's whose life would be at risk were the box to be turned over. I'm surprised your conscience didn't tweak you on that.