A "universal genetic code" is best interpreted as the organic molecular information system that is part of every and all living organisms, most fundamentally within DNA, but having additionally coded elements in other assemblies within the cell.
The complexity and detailed coding of DNA is greater than any existing in any human designed entity, making DNA the logical product of a highly intelligent creator, especially when combined with all of the other detailed elements of a living organism.
There are no naturalistic processes capable of producing anything similar. To prove this, imagine you walk outside and find your name spelled out with small stones in the driveway. You will immediately, absolutely know that some intelligent being spelled it. Now realize that the simplest known organism contains over 1 million coded organic molecules sequenced precisely to encode the proteins and other components within the cell.
As a result, the only rational, logical conclusion for the origin of life is through the utilization of a universal genetic code created by an intelligent designer.