Copyright infringement is mostly dumb, but this is not a good counter-argument.

It reminds me of the halfway paradox (en.wikipedia.org/wiki/Zeno%27s_paradoxes#The_dichotomy_paradox); it’s clever, and I can’t disprove it, but it’s also dumb and doesn’t apply to the real world in any usable way.

Another example, there is no unifying theory in physics. Particle physics seems to work pretty well, as does quantum physics. A person could create a similar grey scale with those, showing a nebulous confusing void between the two, and no one (yet) could challenge it, but that doesn’t mean that either end of the spectrum stops having meaning.