I generally agree, but there are two addenda.

First: Even the worst should be burried with dignity, because their behaviour is not the standard by which we measure our actions. Nobody is so evil that they can take our will to be decent human beings. So we do the right thing (decent burrial) to spite evil.

Second: With dignity is not the same as “with reverence” or “with honor”. In many cultures criminals are denied certain parts of funeral rites (like processions, official or acknowledged mourning periods). This reinforces social norms to the living (don’t do the bad thing or you will be shunned by society) and can also prevent retraumatizing their victims. The most common form of this is not allowing to have their gravesite marked. This is done so that their family may have a place of grief (the unmarked grave) but to prevent the grave from becoming either a shrine to their followers or a target of defilement by the victims. A fairly well known example of the last part is Adolf Hitler who was properly buried in an unknown location and then a parking lot was put over the area with the possible grave sites.