What should I do if my friend runs a Bitcoin business but doesn't understand how it works? My friend doesn't listen to his head of engineering and doesn't fully understand how decentralized consensus based systems like Bitcoin really work. He seems to think a new untested/buggy implementation with conflicting consensus rules can be made to work with the existing implementations that follow existing consensus rules. 

What advice can I give to him?
He should listen to his engineer. I think that's just about it.