> I'd say that you are assuming that optimizing for price is good,

No, capitalism assumes that. HFT traders offer a product to the free market, they sell liquidity and they do it cheaper than their old school competition, there are willing buyers, that is the only justification they require to exist.

> Leverage can be used for good, and sometimes it's used irresponsibly. As this thread's article demonstrates, short selling also creates systemic risk.

Leverage and short selling are different issues, that leverage can be dangerous is not a valid critique of short selling, you're trying to move the goalpost, this is a fallacious argument.

> Eliminating middlemen and/or reducing transaction overhead costs do not require high frequency.

No one said it did, however HFT does do that, which is what was claimed, so again, a fallacious and baseless critique.

> "Buy low, sell high." is the foundation of any successful trading strategy. HFT (when successful) is literally the same thing at much shorter time scales and improved heuristics. Machine learning can probably provide more detailed at a much finer-grain than a simple 10 day sliding window. Again, this does not require high speed.

Again, baseless critique, no one said it required HFT. HFT trading sells liquidity cheaper than those old school simple traders, the market chose HFT.

Do you have any actual critique of HFT, or do you simply presume it's bad and then employ fallacious arguments that X doesn't require HFT? You quite literally have added nothing to the conversation. That it's possible to have a healthy market without HFT is irrelevant, it asserts HFT is bad without evidence, HFT traders have the same right to trade that anyone else does, you don't just get to ban them because you don't like them without cause. That something still works without HFT is not evidence against HFT any more than the fact that I can still travel without a car is evidence against cars.

"Leverage can be used for good, and sometimes it's used irresponsibly. As this thread's article demonstrates, short selling also creates systemic risk."

What critics of short selling are often unaware of is the role that short holdings play in dampening a market crash.

The act of unwinding your short position involves buying the stock which means that for every tick downward in stock price there is new upward pressure on the price as buyers step in to cover their short position.

Were these constant, ready buyers not extant, market downturns can turn into precipitous crashes very quickly.

HFT doesn't front run trades, that's a misconception and really just a way to slander HFT as evil. Calling their misconceptions legitimate is an abuse of language. Front-running is a crime, it has an actual meaning and you are misusing the term. Front-running is when a broker buys or sells using advanced knowledge of trades they're making on behalf of their clients, i.e. it is risk free and is theft. HFT does not front run their clients, they attempt to trade faster than their competition at risk, these are vastly different things and to call HFT front-running is dishonest slander.

There are no legitimate complaints against HFT trading that aren't simply misconceptions about what they do or how markets work.

> Healthy competition optimizes for value, HFT is just optimizing for profit.

Value is measured by profit, if what the HFT's were offering was of no value, there would be no profit in it as no one would buy their liquidity. HFT sell liquidity, that there are willing buyers proves their value. Quite simply, you do not know what you are talking about.

> HFT is just optimizing for profit

And low-frequency trading isn't?