“Science doesn’t know everything” is a classic, common non-sequitur from people defending quackery. It’s true but obvious, and irrelevant to their point … which is that their kooky treatment beliefs are so exotic that they are immune to investigation and criticism, beyond the reach of science. Nope! Not even close!
It’s like declaring a leaky old canoe to be seaworthy because we don’t yet know everything about the depths of the ocean.