Taking the study at face value, it only says that competition among HFT is bad. It also specifically admits that "As market-makers, they can update their price quotes fast when news arrives and provide liquidity to the market. In this case, the low-frequency traders in the market – the investors – benefit from lower transaction costs". In other words, at best it's advocating for some sort of monopoly for HFT, rather than getting rid of HFTs entirely.