Comparing "A" to "B" is nonsensical because moving the goal post does nothing to fulfill the requirement for evidence pertaining to your assessment of "A". If you would assess"A" according to "B", would you then assess "B" according to "C", and "C" according to "D" ad nauseam? Your comparative logic fails because its basically a infinite regress in a "reason costume".
It does allow for gaining insights. Or, to put it in plain English, "getting the point across". The regression implies for a well-stated argument. It helps for credibility.