Okay, I reread the article and I believe he's making the claim that this high explosive can catalyze a thermonuclear reaction more efficiently than the standard explosives on a nuclear device. He seems to be saying that it's possible to bypass the fission stage of a thermonuclear device altogether and substitute red mercury for the plutonium. The claim that it only requires 1000th of the material of a thermonuclear device seems spurious, especially if it lacks a fission stage. The articles rather vague, which inspires suspicion.
I really don't know why he creates this red mercury bogey-man. Standard nuclear technology can create a backpack nuclear device -or Atomic Demolition Munition that could be smuggled into the heart of any major city and take out a large portion of it.