Gold price spikes down, it's the HFT slamming it because they work for the Central Banks. Gold price spikes up, it's because investors are concerned about the market.

Stocks spike up, it's the HFT again. Stocks spike down - investors start seeing that the whole market is a scam.

So the HFT trade only in the "wrong" direction according to ZH. They sell gold and buy stocks. Never the other way around. I'm exaggerating, but only a bit, there were a few articles which blamed HFT for "right" moves (gold up, stocks down).