The liquidity argument is not a "cop-out." Due to algotrading, spreads have been tightened and cost of entry/exit have been lowered. While there are some problems with algorithmic trading, the alternative (going back to the specialist model) is downright insane. If you think algotraders are "ruining" the market and society, then, the specialists and traders were actively scamming everyone.

I'm glad that you have at least done a little bit of research, unlike the majority of articles that came out after Knightmare, but algorithmic trading is a net positive for both the market and society.