Oh, I don't think the stock market should be abolished! It's useful, and I we'd agree there needs to be good regulation and oversight of finance (though we'll always have a revolving-door problem here because oftentimes the only people abreast enough of the scheming to keep a lid on it are the schemers themselves).
I was mainly taking issue with the implication that computer amorality is a problem here. Since these trading bots aren't sapient (afaik; maybe some serious AI specialists would disagree) they're just extensions of human morality. Computers are innately amoral (as yet, anyway). It's the human factor that's sometimes immoral.
If one trusts a computer with huge volumes of money/assets and doesn't know/care about [insert ethical implication of such trust], then they're the problem; a very human problem. Note that a person could, at least in theory, be an ethical, caring, "good" person and still design or participate in a system with a flaw they didn't foresee—cock-up before conspiracy, as they say. Despite spectacular terror-finance headlines, I think most of these people are simply oblivious.
Just to reiterate, if anybody is interested in this stuff I'd suggest economist Mark Blyth, because he writes sympathetically and passionately (and he isn't shy of decrying absolute turds when appropriate, which unfortunately is often).