Mange in Wy is done last few years in most areas. I wish I would have kept pics of the ones I caught like that. We need to keep those and post them on social media out of the traps for folks to look at.
One thing wrong with your theory and makes it easy for the haters . ALL animals will eventually die from disease, hunger or some type of injury. So trapping him as a way to "put them out of their misery" doesn't really hold water from a point of view. BUT it will aid in stopping the spread of the mange so from that angle it could be promoted that you saved more animals.
The year MN had a wolf season. A trapper dropping off fur at my place had a photo of a wolf he trapped that was in the early stages of mange. Proof that wolves in MN were in the beginning stages of overpopulation.
Yes SIr, went to put out hay the other day and there was one froze to death in the hay shed absolutely eat up with the manage. About half of they you catch here have the mange.