Markets should not primarily be a casino.

If you want to invest some of your income into a spread of companies? Go for it. But if all you are doing is trying to game the market? That's just gambling, go to a real casino and have some fun instead.

HFT should be driven by these types of market makers exactly for the purpose of decreasing the amount of unnecessary speculation and volatility in the markets. HFTs killing the spreads is one of the only reasons the markets didn't implode during covid despite the extraordinary fear and volatility that was impacting them.

You want a parasite? Look to hedge funds who just sit on piles of other people's cash to scoop obscene amounts off the top (relative to their actual contribution) for occassionally shuffling funds between financial instruments.

How's that? HFT lowers the barrier of entry for ordinary participants who just want to invest their savings either directly or through something like a pension fund, because they get all those benefits I mentioned, and those benefits are useful when you are only executing a trade once a month or year.

It only increases the barrier to entry to people who want to do HFT themselves on a smaller scale, because they now can't compete on latency etc. But it's a bit of a circular argument to say that it's a bad thing that engaging in HFT increases the barrier of entry to HFT.

In any case, and to reiterate, I wasn't refuting a claim that HFT is a bad thing, I was refuting your original claim that it's pointless. For something to be pointless, there has to be no purpose to it whatsoever, which means it has to have no benefits.

If you're a normal market participant, HFT companies mainly make it harder for someone else to take more money off of the top of your underlying transaction (and you are, in general, going to be paying someone for that). HFT almost completely replaced hoards of the stereotypical wall street traders and I don't really see many people shedding tears for them.