Market makers keep complaining with the Exchanges' managements of how hard liquidity (their business) is suffering because of all this algo trading.
This link is only one of the latest complaints:
Deep Liquidity LiquidityTalks

Some years ago I was persuaded that these algos, these relatively new creatures populating the trading jungle, were very dangerous for the markets and for small traders like me.
With time and further readings I became persuaded that most of the algos are rather challenging market makers (ironically using the same weapons that mm adopted to hunt stops/push prices etc). In my opinion the business model that has been working for decades and that gave market makers a smooth road for consistent profits has finally been challenged and many of them are uncapable (or unwilling) to readapt to the new market reality and to a reduced edge over other predators. This is the main reason why they blame "liquidity takers" and try to restore their edge trying to persuade exchanges to introduce deterring rules. I honestly don't know whether "limiting rules" are the right medicine for markets, or just a shortcut for their own profit goals. In my experience I've always become dubious when I start hearing that there's people "too much" worried of potential damages to the "general public" interest......
I would like to know other opinions on the matter.

They're just pissed that their cartel isn't raking in free money any more.