My manager is currently involved in a special project that I believe is doomed for failure. I know of numerous hurdles that are pretty much impossible to overcome at our level. I've tried to express them to him, but he's gung ho and charging forward. I know I've got a lot of knowledge he could use but ultimately the program will fail (I believe it to my core). I've kind of just pulled back and not really helped and I know he's kind of wondering why. Whenever he asks for my opinion I tell him the hard issues that we're not addressing and he just glosses over them. Any advice?