In this question: Does the impossibility of an infinite regress prove God exists? The argument is claiming that the reason X is an exception to Y's rule, is that Y is impossible, as is. The only way for Y to make sense would be if there was at least 1 exception, or Y is completely wrong. Y being a well accepted aspect of science and philosophy.
How does one navigate such a problem without falling into a special pleading fallacy? Could X really, in fact, be an exception due to the circumstances?