The only few people who defend HFTs have vested interest in doing so.
Objectively speaking, it is not trading... it is vampire leaching from order flow and true open interest. Algos do not create liquidity, they drain true liquidity.
To the people who admonish others about adapting: surviving traders have already adapted to the HFT/algo world. They adapted by trading smaller size and more round turns to combat the incessant counter-swing bursts and random spikes & slams that exist only because some bot is spreading futures against shares in liquidity-drain fashion.
Remember all the guys back in 2008 who gloated about $100k days and seven-figure profits? Where are all those big gains now? Same guys are still in the game... but they cannot work same size as three years ago. The tapes are much more erratic because of the illiquidity.
It's not that anyone cannot fill 100-lot ES... the fact is, who the hell wants to? The next real flash-crash will happen again, it'll happen soon and this time it will not recover intraday. When the next algo-driven crash hits this current market, it will finish the day off -1,000 index points on the Dow.
HFT is nothing but another temporary fad in the market. It ain't trading, it's just loopholed order flow theft and nothing more. HFT guys don't know the first thing about real trading, any more than SOES bandits did.
Same game, different era, same inevitable end.