I cannot fathom a society that puts pets 'to sleep' (kills them) and says how it was the right thing, but cannot comprehend that perhaps sane minded humans might want to be spared the same suffering that we take animals on their final journeys to end.
Because we don't worry if we kill a pet that was actually a happy pet, but if we kill a human that was actually happy, then we've murdered someone. Obviously people can then debate whether or not someone is happy before possibly killing them, but that's pretty messed up.