I agree with it. I'd persoanlly hate to be clinging to life in a vegetative state...that's no way to live at all.
If the person is conscious, then I agree with that, too. Assuming they put some thought into it and it's not just some rash impulse, it's their life. A person's life is in their own hands, I don't think anyone else has a right to choose for them.
If their suffering is that great, it seems cruel (and a little selfish, really) to deny them.
We do it with pets, so I don't see why it's so terrible to do it to a person.
Anyway, I don't really think you can say it makes a person 'grow' until you've experienced their pain. And really, if I were in terminal pain, what do I care about growing? :S