That's a very large leap. I think it's pretty clear that there's a difference between necrophilia and saving people's lives. Even if there weren't, you're still giving people a mechanism to defend themselves from such behavior. This is not the case in necrophilia.
And? That doesn't mean anything about if it's moral or not, so it's irrelevant. Unless you assume that what makes something moral is "what everyone does", which is in-correct by the definition of "moral".