I am very sorry about the death of this young lad, and the other guy.
Part of being a licenced pilot is knowing "when to say no"....regardless of what other people say. In the past I have accepted "free" flights and I remember one in particular which scared me. I now have a very good appreciation of what I'm getting involved with and will say no if I think the risk is too high. If I go then I accept any consequences.
Unfortunately it takes some time to learn this, usually through the mistakes of others and BBS's like Pprune which is a great asset. Peer pressure can play a part too, but again it goes back to the first line of paragraph 2.