Even the taking of liquidity in the anticipation of a price move is not inherently bad. It is only bad if it degrades market efficiency (for example, by adding instability). An aggressive order that anticipates a price move due to an existing market inefficiency (for example, a sudden over-reaction to a report) benefits the market by speeding price discovery and adding stability.

As to your question of how an aggressive HFT strategy could benefit Vanguard, consider that if Vanguard places a passive order, it is because Vanguard hopes to attract an aggressive matching order. If they are unable to attract one within their time requirement, they will likely need to change their order to a less-profitable price. Their time requirement could be quite short during times of great volatility. An HFT strategy able to more-quickly recognize that Vanguard's original price was attractive would save Vanguard the cost of a price change. This benefit can be particularly large during significant market stress when participants are forced to liquidate assets in order to manage risk.

Is there evidence for this?

"the field contributes nothing to society, and has only negative externalities"

I believe that the rise of importance of finance has been a net good for humanity, but I know that's an unpopular opinion and I've seen good arguments that it's a net harm. But I don't think you can make a reasonable argument that we could have a modern world anything like the current one without stock markets. Banks and credit unions don't, can't and shouldn't provide the kind of funding that equity markets do.

Not really. A financial system that only consisted of debt and not equity would not be able to support anything like our current economy. We would all be much poorer for it. Loans are simply not suitable for a huge variety of financial risks.

https://www.chron.com/neighborhood/bayarea/news/amp/When-Bor...

Did you notice the breadlines in the US earlier this year?