First off, my quibbles about the definition of front running vs predatory trading are unrelated to my defense. The defense I gave was about price discrimination. It doesn't matter what label you apply to the definition - if you want to argue against me then say why price discrimination is bad. Or say I'm wrong about price discrimination.

Second, the "spirit of the regulation" about front running is about allowing people to trust their agents. Other regulations in the same spirit are lawyer-client confidentiality and "financial advisers can't take gifts from companies they give advice on" regulations.

There are no "you can't kick people's ass in the stock market" regulations, in letter or spirit. If you play the stock market everyone is trying to take your money. You are trying to take theirs.