Lol, suit yourself for misrepresenting your problem.
If your friend keeps poisoning himself and do not alter his behavior when he notices it is killing him he is either trolling you or he is borderline retarded.

Your friend not understanding the concept of poison is nothing Larian can change with coding.

Have him pick zombie as well and then you both can heal from poison. Or teach your friend what he fails to learn, or play with someone who wont troll you.