If a government official can break one of their own, very serious laws, get caught red-handed, and openly get away with it without facing any real repercussions, then yes, the rule of law is dead. At that point the law is only selectively applied and enforced, which isn't the rule of law at all.
Let me know when one of you makes a decent argument to the contrary that doesn't involve simple hand-waving.
If your rule of law allows pardons to be granted, and a pardon is legally granted, then that is not the death of the rule of law - that is, arguably, bad law.
If the offense is relatively minor, or is of a type that is often overlooked then it is not particularly remarkable at all.
If the offence has been "ignored" based on influence, malfeasance of office, corruption or similar illegal activities then that is simply illegal and is still not the death of the rule of law.
In practice the rule of law means that individuals are subject to the law - it does not mean that all crimes are punished all the time, and the illegal or immoral selective application of the law speaks moer to the rule of law still being in force, rather than any individual being above the law.
Back to the original point - whether the UCC makes the constitution irrelevant - I don't know if it has been mentioned yet, but my understanding is that the Constitution is not actually law. Rather it is the set of principles by which the USA will be governed, and as such it requires laws to give it effect.
The UCC is one part of that set of laws.
Therefore the UCC cannot possibly supercede the constitution, by definition.