"If "cold fusion" didn't violate so many laws of physics, and were a real phenomenon, we'd have seen it already in nature."Actually, there is quite a bit of evidence that we "have" seen it in nature.
Prove it. Other than muon catalyzed cold fusion there is nothing accepted by science.
The muon process takes a ton of energy (figuratively speaking). It isn't a source of energy.
You can also achieve a sort of fusion by bombarding atoms with neutrons. Again, this process does not release energy. Its use is to make radioisotopes for medicine and medical research.
Fusion, in the sense of pushing two charged atomic nuclei together to force them to fuse, is impossible except at really high temperature (i.e. at high energy), and only small charged atoms can be fused in this way. There is not sufficient energy in the galaxy to fuse large atoms together.