Arguable whether or not HFT increases liquidity in the market.
It is arguable if more liquidity is a good or a bad thing from some sides, but I'm not sure how HFT increasing liquidity was ever a question? It is a matter of volume and there is more automated than non-automated volume in most equities and futures exchanges.
However, given that you want to make a trade, it's not arguable whether you want more market participants or fewer.
It is "beating the market" if your strategy results in higher net fee-adjusted returns than the overall market (typically ~7-11%). But yes it's different because you're not deploying a trading strategy, you're being a market maker for other traders.