I think I know where the confusion comes from, granted in saying so my information about Archangel Samael is very small. However, from sources he does seem like an angle of health as will as Death. He most likely helps guide the dead to the spirit world and comforts them after their time on Earth has ended. In many sources he is still seen as an angel of the divine.
Is he a demon? Probably not, but if he is seen as someone with change and death in his title. Than this is where the demon part might have came from. We're not very good with change, we fear the things we cannot understand, so this is where the confusion may have came from. Many angels are known to protect people fromviolence.