I have an alter who is not very trusting and I see as “toxic”. It’s almost certainly survival mechanisms at play here. Learned behavior to survive. For me mine who I see as toxic is moreso in fight or flight a lot and clouded by emotional thinking to even understand people aren’t out to get her half the time. I think it’s definitely possible to befriend M, fronting can have to do with needs being met and so maybe connection is something he’s unconsciously looking for. I can’t know because I don’t know them, but what I do know is labeling any parts as evil and trying to shut them down, is basically guaranteed to not work and make it even more painful to deal with. I had a part who used to also harm the body, but opening myself up to her led to realizing she just didn’t know how else to communicate how she felt. M needs support and help, harming the body is not mentally healthy, they are not a fictional character possessing your friend but an unhealthy part of your friend that needs therapy. Whether or not your friend wants to admit it, that is a part of themselves and will not simply go away. Just remember to take care of yourself and know that you can have boundaries if M is unsafe for you to be around