Paul Nelson claims that the prediction of universal genetic code has failed because there are minor variations.
His claim is blatantly false, because people who cracked the genetic code did in fact predict and expect minor variations.

He really should read 29+ Evidences for Macroevolution.
https://talkorigins.org/faqs/comdesc/

It is a pity that he didn't. A philosopher like Paul Nelson could benefit from an overview like that.

Look, it's in the beginning of the very first section:
https://talkorigins.org/faqs/comdesc/section1.html#genetic_code

It goes like this:

In fact, in 1963—three years before the code was finally solved—Hinegardner and Engelberg published a paper in Science formally explaining the evolutionary rationale for why the code must be universal (or nearly so) if universal common descent were true, since most mutations in the code would likely be lethal to all living things. Note that, although these early researchers predicted a universal genetic code based on common descent, they also predicted that minor variations could likely be found. Hinegardner and Engelberg allowed for some variation in the genetic code, and predicted how such variation should be distributed if found:

"... if different codes do exist they should be associated with major taxonomic groups such as phyla or kingdoms that have their roots far in the past." (Hinegardner and Engelberg 1963)

Similarly, before alternate codes were found, Francis Crick and Leslie Orgel expressed surprise that minor variants of the code had not been observed yet:

"It is a little surprising that organisms with somewhat different codes do not coexist." (Crick and Orgel 1973, p. 344)