The largest HFT firms are not banks. Banks have largely spun off their HFT groups, like Process Driven Trading from Morgan Stanley. They are independent firms like RenTech, Getco, Citadel, Tradebot, etc...
They are not really any different then the pit traders they replaced. Pit traders paid to be "co-located" at the exchange because they could trade with "lower latency".
With RegNMS HFT firms provide a valuable service making sure that the price of a security is more or less the same price on all exchanges. Many firms (like Getco) have official market making responsibilities.
HFT is not theft. There are abuses, like layering, which should absolutely be prosecuted. Market making has always been about speed and always will be regardless of what rules are passed.