It is a good idea to tag sufferers of dementia. Too often, we read stories in the newspaper about an elderly person with dementia wandering off and a manhunt called to find them. Sometimes, it ends in tragedy. It would be more assuring for the caregivers and for the police to be able to find these people quickly and bring them back to safety and I do not consider it a violation of their rights.
Dementia sufferers often aren't in control of their own bodies. As such, the power of attorney is often given to another person when someone can't take care of themselves. People with dementia should be tagged to make it easier for caregivers to find them if the person gets lost. Someone who is losing his/her mind needs all the help they can get, regardless of possible civil rights violations. Plus, electronic tagging may save someone's life.