That's not right. Dignity is "the state or quality of being worthy of honor or respect". Someone has (or doesn't have) dignity irrespective of how they are treated.
I think it's trivially obvious that some people do not deserve to be treated with dignity (e.g. child molesters, mass murderers, etc.). The fact that you treat them with dignity in spite of that is obviously virtuous, but they don't deserve it. As opposed to people that do: Gandhi, Jesus, MLK, and so on.
> it's trivially obvious that some people do not deserve to be treated with dignity
I don't agree, and I know many people who also would disagree. Another point of view is that perhaps some people don't deserve dignity, but I'm not knowledgeable enough to know which ones and only an omniscient supernatural being would know enough to make that judgment.
For me, this is the most memorable statement that concept; probably not the best, but it's where I first grasped it:[0]
Frodo: It's a pity Bilbo didn't kill him when he had the chance.
Gandalf: Pity? It was pity that stayed Bilbo's hand. Many that live deserve death. Some that die deserve life. Can you give it to them, Frodo? Do not be too eager to deal out death in judgment. Even the very wise cannot see all ends.
Also, I don't know of anyone who should throw stones. I hope I'm treated with dignity when I make mistakes; certainly nothing is gained when I'm not.
[0] There are at least a couple variations I found in a quick search; don't take this one as authoritative.
