All HFT is blackhat, leeching off flaws in the way the market clears. There's no legitimate value to be offered by interposing between a buyer and a seller who are in the market simultaneously and would have done the trade unhindered. Traders are a net win for society if they cause better resource allocation, not the same allocation a fraction of a second sooner thanks to a greater misinvestment in network hardware.

Batches of buy and sell orders which are in the money should be executed hourly. The fundamental values of companies don't change more quickly than that. The rest is noise, not signal.