Choosing to believe

Sometimes I conclude that our disagreements are based on what facts we choose to believe.

Why do some people want or choose to believe "facts" that others have already proven to be myths or lies? For example, www.snopes.com and others regularly research and shoot down myths that many folks continue to believe. Also for example, many people believe our President lied about the WMD in Iraq, and I admit we have found little evidence of them. On the other hand, I, and many other Americans, continue to believe that Saddam had WMD. That sounds irrational to me.