It makes sense, right? If you believe something, then, you would argue that it’s real. If you doubt something, then, you would hesitate to affirm it as real. Certainty works the same way as doubt, but with total affirmation. In other words, doubt is a bit malleable or flexible and allows for further consideration, whereas certainty hardens into a concrete form. One who doubts something, then, may listen to and consider an argument for an opposing opinion; one who feels certain of an opinion or belief will not.
Over time, unevidenced arguments can affirm doubt and increase the certainty with which a person holds an opinion, whereas evidence in any form may erode doubt when applied against the opinion, or affirm doubt when offered in its support. To argue against doubt while unarmed with verification works against your cause and does it harm in the doubter’s mind. To argue against certainty accomplishes nothing. You may chip away some fragments, but they will be quickly patched.