We euthanise dogs, why not humans?

When speaking with someone who is in favour of legalising euthanasia by far the most common comment that I have heard goes something like this, "We don't even let our dogs die in pain like that- we have euthanasia for dogs, why not humans?"It is one of the most common comments I hear, and it is also one of the most ridiculous.The answer should be obvious; humans and dogs are different and the fact that their lives should be valued differently should be obvious, and yet somehow this needs to be explained and often the conversation can very quickly lose track and devolve to attempting to ascertain the philosophical difference between the life of a dog and the life of the human.It is frustrating because I know that (usually) the person I am talking to actually agrees with me in practice: in their daily life they do not treat dogs with same dignity with which they treat human beings, and yet getting this message across can be surprisingly difficult.What you need is a short response which will bring the conversation back where you want it:"Yes we do have euthanasia for our animals who are sick and suffering, we also have euthanasia for those of our pets who we cannot look after anymore, who are found unwanted and unclaimed on the street. Is this what you want for humans? Should those elderly who are dependent on others be at the mercy of those who care for them as to whether they live or are killed?"Normally this response is met with outrage,"Oh no! You're intentionally misunderstanding me, that is a strawman, no one is advocating for that." "So pets and humans should be treated differently then?"Then you can go on discussing your arguments against the legalisation of euthanasia.