Can't you just talk to him directly? Present your arguments in an honest and respectful way, then see what his reaction will be. There's a good chance that you

Can't you just talk to him directly? Present your arguments in an honest and respectful way, then see what his reaction will be. There's a good chance that you will be able to resolve the situation without much of a fuss. He might even appreciate the feedback. When things go side-track (i.e. really bad) talk to his supervisor.