Sometimes you can. I used to be a young-earth creationist, but I'm not any longer, not by a long shot.

My transition came in several steps. First, I was shown that my belief in a young earth was incorrect due to reason and the scientific method while I was in college. I finally admitted that I was opposed to evolution for no other reason than because my teachers and parents had told me so. At that point I became an Old-earth creationist, believing that God created all life and that he used evolution as his primary tool.

That settled the issue for me for a while, although when I thought too much about it, it seemed disquieting. I couldn't understand why God would create a world that appears not to have been created. But I continued to have faith in the matter and looked forward to the day when I would "get smart enough" to understand it.

A decade later, I lost my faith in faith. I no longer see faith as a valid means of obtaining information. I only believe that which my reason tells me so, and I leave my mind open for new data.

So it's possible to reason someone out of an irrational belief, but in my case it took nearly fifteen years.

Note, if the religious tone of this post violates forum rules, pull it at once. I have no objection.