There may, of course, be other nonlogical considerations which lead one to grant that it would be pointless to hold some particular view as being open to criticism. It would, for instance, be a bit silly for me to maintain that I held some statements that I might make—e.g., "I am over two years old"—open to criticism and revision.The claim that some statements are beyond criticism is anti-fallibilist and anti-Popperian.
Yet the fact that some statements are in some sense like this "beyond criticism" is irrelevant to our problems of relativism, fideism, and scepticism.
It is not at all silly to maintain that the example statement is open to criticism. It's essential. Not doing so would be deeply irrational. We can make mistakes, and denying that has consequences, e.g. we'll wonder: how do we know which things we can't be mistaken about? And that question begs for an authoritarian, as well as false, answer.
You may be thinking, "Yes, Elliot, but you are over two years old, and we both know it, and you can't think of a single way that might be false." But I can.
For example, my understanding of time could contain a mistake. Is that a ridiculous possibility? It is not. Most people today have large mistakes in their understanding of time (and of space)! Einstein and other physicists discovered that and space are connected and it's weird and doesn't follow common sense. For example, the common sense concept of two things happening simultaneously at different places is a mistake: what appears simultaneous actually depends where you watch from. If some common sense notions of time can be mistaken, why laugh off the possibility that our way of keeping track of how much time has passed contains a mistake?
Another issue is when you start counting. At conception? Most people would say at birth. But why birth? Maybe we should start counting from the time Bartley was a person. That may have been before or after birth. According to many people, brain development doesn't finish until age 20 or so. In that case, a 21 year old might only have been a full person for one year.
Of course there are plenty of other ways the statement could be mistaken. We must keep an open mind to them so that when someone has a new, counter-intuitive idea we don't just laugh at him but listen. Sure the guy might be a crank, but if we ignore all such ideas that will include the good ones.