Honestly I don’t think they should be involved in social change because sometimes it’s not good...for example let’s say the person is fine with him/her self so they now need to change, that messes up their mental health and maybe their confidence in doing things. Because now they are gonna worry about what other think of them.
Rainsford does not hold human life on the same level as animal life. For Rainsford hunting is a sport or a means to gain food, not a mere even to simply kill for the love of killing.
Zaroff's ideas counter this in that Zaroff has progressed to the point where killing humans, the most intelligent beings, has become a sport to him.
The bottom line is that the two men have different world views which influence their actions.
The guy was suffering in life but he still had love and care for his sister to say happy birthday. It shows how mental health is not affected by how you live your life. It's not affected by a lavish life but rather its what your mind thinks is what your mental health leads to.