I think dignity is something you have until you prove you're unworthy of it, by behaving foolishly usually. But anyone can have it, from a beggar to a doctor.

All people should be treated with respect and dignity, regardless of their circumstances or what they’ve done. It’s not because we are trying to be good people or a fair society. It’s because IMO such treatment is a logical necessity.

Every person alive is the culmination of a long line of survivors. That fact alone should elicit respect, but beyond that we are all joined by common awareness IMO. I can not disrespect another person without disrespecting myself. Basically, every person is a wonderous miracle,

No matter, if someone has become a threat it is a duty to deal with that threat—efficiently but not with hatred or anger. For society to function there have to be rules, and there need to be penalties for breaking those rules. But that is a different subject.

All people deserve to be teated with dignity and respect. But, when one behaves selfishly and/or destructively on a consistent basis, society has good reason to withdraw that respect.

I think the useages of the term Dignity are being conflated.

1. the state or quality of being worthy of honor or respect.--Ancient Roma
2. a sense of pride in oneself; self-respect.-- The sense of "Human Dignity" you claim modern Liberal Democracies insist upon, that every human being deserves some respect by default, a modicum of Dignity.

I think dignity is a word that is confusing. We all know how to act in a dignified manner, by our demeanour , we conduct ourselves in a civil and polite way towards others, therefore conferring them with dignity. So by showing this example it is twofold, it is something we can both confer on ourselves and on others.