I have been interdicted in by a human in Open play only once and this was when I was in an Asp with 100 odd tons of rares, the Clipper CMDR told me to drop cargo or get served, I obliged and dropped 1 item, he said "that'll do pig" and forked off. Could I have taken him with the Asp? Could I have legged it without dropping a Leathery Egg? No to both, no guns and heavily weighed down with shields and hull reinforcements. The only thing that made me get narked was the "that'll do pig" comment. 2 minutes later I was laughing at it.
As for the CMDR that started the thread, what are you doing leaving your wingman behind and unprotected in OP. With you flying in a Python you know your safe...sort of, but a Novice in a pesky 'lil sidewinder stands no chance TBH ESPECIALLY at a RES. You should have taught him the way to use Wings from the start (nav lock and beacon) and BOTH gone into the RES. If it was pants then you could have left and returned like you said you were going to, or jumped to another RES in the System.
Your mate died at the hands of a "superior" pilot because you were trying to be too safe. Sorry if it sounds hard, but its true. Make a Private Group, invite ya buddy, then go from there, if he had started from the BETA, Gamma or release then he wouldnt have had this happen. It's like someone now buying (i'll use the obvious examples) Battlefield 4 or CoD:AW (both are pish IMHO) and thinking they will have a good time...they wont, they will get spannered every single round and wont enjoy the game as the old timers have better weapons, like you in your Python...(I don't even have a Python). Don't let him give up, when your not around tell him play in Solo and make the dosh that way, at least he will only have to worry about NPC pirates, and if he is too nervous about fighting them tell him to set full engines before he jumps to SC, throttle back to zero if he gets interdicted then get ready to leg it and as soon as he can SC away again. He will learn to enjoy it like the rest that play it no doubt