[traK6Dcm]

Even if that was true (it's difficult to prove either way since there is little data on black swan events), the fact that they provide liquidity during stable times can make up for not providing liquidity during black swans. The impact could still be net-positive.

Also, it's unclear what the alternative is. While HFT may not be needed, markets run by human traders were significantly more unfair than anything we have now. It's just that fewer people complained about it because nothing was transparent. Or do you believe human traders don't pull quotes?

[jliptzin]

I don't really have an opinion on how to make the market fair one way or another, I just advocate for retail investors to completely dispense with the idea that the market will be fair to them. I see a lot of people getting into day trading not realizing that the whole thing is completely rigged, from front-runners, insider traders, hedge fund managers with huge pockets spreading fake news (watch Jim Cramer brag about all his different market manipulation tactics: https://www.youtube.com/watch?v=gMShFx5rThI), etc. Unless you are prepared to engage in that kind of behavior as well (and have the resources to do it), expect to lose your money. Your only option is to buy and hold for the very long term.