The problem with HFT is that it's unfair and discourages investor participation. A batch auction system would level the playing field. Obviously, HFT is currently legal and profitable; I'm talking about reforming the market.
I'm sure HFT does dissuade a class of day traders from participating in the market. But who cares? Electronic trading also killed the human market makers, who simply got outcompeted. The result, again, was an unalloyed good: the human market makers were crooked as a wallet full of 3 dollar bills.