When people disagree, they can be vehement, vocal and loud. They often back up their disagreement with emotion, facts and reason.
When these people are presented with evidence that is contrary to their belief, how do they respond?
Do they change their mind? Are they now vehement proponents of an idea that they once vehemently opposed? Do they now support the idea with the same force that they once opposed it?
We have the right to firmly oppose an idea. But in the face of evidence to the contrary, we also have the duty to change our mind.