Peachy, that is really sad about your dh. But still clearly a difference between him trying to commit suicide and you deciding off your own bat that 'because you are disabled or because you are depressed, I am going to kill you', without even consulting him.
I think there might be circumstances under which I could kill myself. But I can't see myself taking that decision for somebody else.
For some people, of course, there is a direct relation between disability and depression: dd is only ever depressed when she is in pain or feeling unwell. But I still agree with you, Riven, that there is a tendency to put everything down to disability and somehow to see that as different to anything else that life can throw at you. Of course, it is sad that dd is depressed because she is in pain. But possibly not worse than my brother being depressed last year because of his messy divorce and subsequent alienation from his children. And I don't think anyone was really thinking in terms of a mercy killing, then.
The thing is, people kill themselves for all sorts of reasons: bad finances, career failures, marriages breaking down, ill health, abuse or trauma. But when did you ever hear of anyone who thought the kindest way to help the victim of sexual abuse or alienated father out of their misery would be to slip a little something into their tea? You just don't hear of that at all.
I am pretty sure that if I tried to relieve dd of her sufferings, noone would have any doubt that I was a murderess- despite the fact dd (unlike many disabled people) fulfills the criterion of genuine pain and suffering. And I can think of no other reason for this than that dd is a verbal communicating ordinary looking person who reminds NT people of themselves. So it's not actually about suffering, is it?
It's not really about mental capacity, either. If it was, then half the inmates of MIL's care home would have gone long ago. But then we all know, don't we, that we might end up senile one day, and we don't particularly fancy the idea that someone may be merciful to us...
It is about disabled people as "the other", in a place where we can't imagine ourselves.