What's so bad about this? Other trading firms are also using HFTs. I assume Robinhood is making more because they have more trading than other companies. It sounds like a good strategy. I don't see a red flag in this.
If this is the implicit assumption, the article still falls victim of a slippery slope fallacy by letting readers believe “if Robinhood does this, what other companies can sprout up to encourage HFT exploitation?” Regardless, the article points to a good discussion in the direction of “at what point do we expect HFT to be the only way to benefit from the stock market?”
What's even more surprising is that other company like E-Trade costs money AND they sell it to HFTs.