how to save a friend

Some people are never going to listen to reason. I think what you should do is simply share your thoughts and just leave it at that. If something happens, you can always say: I warned you about that! If you push too hard your friend won't like it and will walk away. There is no way you could help them after that! Good luck with your situation! It is always hard to see a friend get hurt but sometimes there is little we can do!

i think that thing that you can do is to support his decision. i think that least that he needs from you is you not to agree on his decisions. i understand that you are speaking for his sake but i think you at some point need to realize that he wants to make decisions for himself. just be there to support him. whatever happens. whatever "may" happen. he may end up hurting and all that, be sure to be by his side always, not contradicting his decisions but always being there for whatever happens.