I think you are misunderstanding the article. Perhaps re-read it. The point is that bitcoin does not spend enough energy to protect the network. Bitcoin mining

I think you are misunderstanding the article. Perhaps re-read it. The point is that bitcoin does not spend enough energy to protect the network. Bitcoin mining is not comparable to gold mining because the purpose of bitcoin mining is to secure the network's transactions, the fact that bitcoin mining produces bitcoin is merely a side-effect of this. If gold mining ceases to exist, or if a single company dominates the world's gold mines, that doesn't prevent people from moving gold ingots around. It doesn't allow the gold mining monopoly to double spend. But this is true of bitcoin. So it's unwise to make such a comparison.