Yeah that would be disrespectful. Kind of moving the goalposts though to use that example when talking about organ transplant, something that helps people who might otherwise die. Obviously I am not saying execution is worth it for that. Just more that if someone is dead already for whatever reason, it's hard to see it as a bad thing to help the living, if that can be done.
I mean if we're going to fashion extreme examples for dramatic effect, that can be done on the other side too. Imagine if the relatives have racist objections to donating an organ, and let someone die because their own feelings would be hurt if they saw a person of the "wrong" race being helped. How do you weigh their racist feelings, versus the life being saved? It's not that clear to me that their feelings should be at the forefront when other factors are considered.
I agree that dignity in death is a good thing. Just not so certain as you that there is only one way to get there. And none of this is to claim that China does what they do with dignity... I highly doubt that. But organ transplants are not such a terrible thing.