We have a duty to treat the dead with dignity as a duty deriving from our good will, independent of religious considerations or concerns of virtue.

Evidence

Our Duty to the Dead (Philosophy Now)

corroborated: 2 independent passages support this claim
XREF: connects to: Small acts of decorum toward corpses matter more than practical logic — Julien Gracq, Balcony in the Forest, 483; We should respect corpses because violating them would be a violation of human dignity, and it is still a violation — What is the philosophical basis for respect of human corpses; Moral and philosophical conceptions of dignity hold that a human being is entitled to ethical treatment in all phases of life and even through death. — Dignity After Death and Protecting the Sanctity of Human Remains (+2 more)

We should respect corpses because violating them would be a violation of human dignity, and it is still a violation (similarity 0.88)
Moral and philosophical conceptions of dignity hold that a human being is entitled to ethical treatment in all phases of life and even through death. (similarity 0.87)
Not all legal regulations regarding treatment of human corpses are spelled out in the language of dignity; some offenses express special disrespect against the deceased (similarity 0.85)
Posthumous dignity is not a right held by the dead but is the reason why the living have duties of respect and protection toward the dead. (similarity 0.85)
Posthumous dignity is not a right; the dead do not have rights and therefore no right to either posthumous dignity or posthumous respect. (similarity 0.84)
There are no practical reasons to show respect for the dead - you don’t get anything and the person is dead, so it makes no sense (similarity 0.83)