Jeff Lash counsels product managers to embrace, or at least not discourage, bad ideas. Team members provide ideas and suggestions about how to develop, market, and sell products. A fundamental part of fostering innovation is to encourage the free flow of ideas, good or bad.
I would go so far as to add that your product manager should actively and intentionally be introducing bad ideas of his own. Doing so breaks the ice so that team members won't be afraid of introducing the first bad idea. It also puts team members in a counterintuitive state of mind, which is conducive to innovation.