At what point does public discussion of someone's religious views become a discussion of potential mental illness or compromised reality?

This almost went to politics, but it's probably better here. A very current example would be a political ad describing how Mitt Romney (and other Mormons) believe that they may become gods, which could be construed to suggest an unstable mental state. After all, a secular politician who said he believed that he may become a god in the near future would be labeled a crackpot at best, and a man telling a cop the same thing on a street corner might be locked up for observation or at the least thought to be unstable.

So where is the line drawn between pointing out potential mental health and/or judgement problems and "attacking" someone for their religious beliefs?