I agree, and I think this is probably the most effective method, and is generally what "polite" behavior is supposed to be. In etiquette it is considered poor manners to simply tell people, straight to their face, that they are mistaken unless they specifically asked for an honest opinion.

http://en.wikipedia.org/wiki/Politeness#Techniques_to_show_politeness

I suspect politeness is the most effective method to deal with 'people who are totally wrong' because it is very rare to actually convince someone else they are wrong. It is much easier for people to change their own minds, then have an outsider change it for them.