The distinguishing characteristic of rationalization is that it attempts to obscure the difference between truth and falsehood so that we can no longer reliably distinguish between the two. For example, a common Christian apologetic claims that we can never know whether, say, the 9/11 terrorist attacks were inconsistent with the idea of a loving, omnipotent, and omniscient Heavenly Father. God is (supposedly) so much wiser than we are, and knows so much more than we do, that we can never question His wisdom in allowing evil things to happen. Even though it might seem obvious that a good Person would have acted to prevent it, we can never know that God was wrong/negligent to fail to intervene, because God might know something we don’t.
The argument, in other words, is that because of human limitations, we can never know what the right answer is, and therefore we can never say that anyone else’s answer is the wrong one. But that’s a false argument, as we can see by looking at the number pi.
Pi is an irrational number, which means it cannot be represented as a ratio of two integers. In decimal notation, it’s the number 3 followed by an infinite series of digits that do not repeat. We can never know the exact value of pi down to the last decimal place because pi doesn’t have a last decimal place. God Himself could not know the exact value of pi down to the last decimal place.
The fact that we cannot know the correct value of pi, however, does not mean we cannot recognize values that are incorrect. If you say that pi is 3.14…, you haven’t given the exact, correct value of pi, but at least the digits you’ve given are correct so far. Pi is not 3.19… or 3.11…, and it’s definitely not 157.27…. To the nearest 3 decimal places, pi is indeed 3.14, and is not 3.15 or -8.99. We may not know all the right digits, but we can recognize wrong ones anyway.
It’s the same with God. We may not know everything an omniscient God would know, but that doesn’t prevent us from recognizing that it’s wrong to withhold information about a terrorist plot that is going to cost thousands of innocent lives, or that it’s similarly wrong to watch people suffering from diseases that would be curable if only you would share your knowledge of the cure. We may not know the exact value of pi, but we know it’s not 77 million and something, and we can recognize an abject failure to undertake even the most minimally moral opposition to evil, even without knowing everything an omniscient God would know.
The point of the apologetic is to rationalize evil, i.e. to deprive us of the ability use real-world evidence to distinguish between truth and falsehood about God. But it’s a failed rationalization. We all know that conditions in the real world are not the conditions that would result from a real, omnipotent, loving God. It’s just that some of us try to rationalize away the problem.