The average investor holds onto stocks for months to years. A flash crash may last minutes, before the price is back where it was. How does a flash crash hurt the average investor?
> Not to mention the practice of front-running and other shady practices that HFT's use to make profit.
Front running is where a broker or other agent trades on private information given to them by their client: the broker receives a big buy order from their client and then buys the market up on their own account before executing the client order and making a massive profit. This is illegal.
HFTs can't front run - they only have the same public information at the same time as everyone else. The fact they can execute on that faster than others hardly seems 'shady'.