I appreciate your civility...that's actually exceedingly rare on this site. I agree that some HFTs have and probably still do engage in manipulative activities, but I'm adamant that cancelling orders isn't morally wrong. Placing orders you intend to cancel is wrong, but placing orders with the intent to trade and later cancelling them because you no longer intend to trade at a given price is just something totally different. If cancelling orders was wrong on its own, why would regulators even let you do it?