There may be a few, but there are countless more who falsely believe this about themselves. Therefore it is wiser in most cases, especially one's own, to presume that this belief is self-deception. Self-observation quickly reveals how often the emotional reaction precedes and conditions the cognitive one.
If someone can show a track record of having changed their views, and their arguments are from the perspective of achieving a greater understanding, and not of cramming some ideology down others' throats, I'm markedly more willing to consider that they are sincere in this statement.
It's not necessary to bend in every wind, but I look for some signs of adaptability.