Actual front running requires your broker to violate the fiduciary responsibility they have to you, and violating fiduciary responsibilities is both immoral and illegal.
The behaviour your discussing does not involve any fiduciary responsibilities.
> This behavior, however, is identical to it in spirit and moral character.
That seems self-evidently false, but okay, I'll bite: What moral precept is being violated here, and why is it "identical" to the fairly serious sin of someone with a fiduciary responsibility to you violating your trust?
Let's play fill in the blanks: "Goldman Sachs wants to buy $400m stock in Apple, but after they buy $20m, a member of the public sees the strange pattern of executed orders, guesses that someone is buying a lot of Apple stock, and starts buying up stock too. This is highly immoral, because members of the public have a ______ duty to ______, and not allowing Goldman Sachs to manipulate the market in peace violates it."
What phrases can we put in the blanks that makes that not nonsense? I'm pretty sure it's not a fiduciary duty, and it seems quite clear it's not to Goldman. What duty is it, and to whom is it owed?