They try to make it as humane as possible.
However, its just as cruel to watch a horse die of starvation, or be in such pain but the owners can't afford to euthanize it. I am curious what you consider bad conditions?
I just got done shooting and slaughtering two steers. They dropped in their grain buckets and until they bled out, their muscles etc jerked and moved, yet there were dead, no eye movement or motion. Do you consider this cruel also?
Or is it because its okay to kill a steer, but not a horse? A shot to the head is fast and quick. I have also been involved in many euthanizing of horses, it is usually very fast and quick, but I have seen ones go wrong and it takes longer than normal. Guess that is considered cruel also.
It might disgust you that the bill was opened again, BUT, since I doubt you or anyone else has the land/feed necessary to keep all the old, sick, injured or whatever else condition horses for their lifetime. Years ago people could afford to keep horses as yard ornaments for their lifetime, now the economy makes it very difficult to do.
I would rather seen horse slaughter done again that watch the way people treat the same horse: let it starve, turn it loose to see wild animals eat it, dogs chase them for sport through fences, or just take it on public land somewhere and leave it and drive off, after all, is a horse so it should be able to fend for itself
A trip in a trailer and a quick bullet is much faster than other scenerios.