His main point: Wall Street doesn’t know what business it is in. Wall Street has nothing to do with creating capital for businesses, its original goal.
He's saying wall street should have an incentive to create/raise capital for businesses, not invest in marginally profitable trading strategies like HFT.
The opportunity cost of wall street investing in trading is that other pursuits like capital raising get less or no attention.
So it's not that HFT is necessarily good or bad, it's that it's a distraction that's not going away, to the detriment of other potentially more value-creating pursuits, like raising capital for new companies.