C'ote D'azur,
"If all "speculation" was outlawed tomorrow (very easy to do)"
Actually, almost impossible to do! How can you separate out speculation from hedging. Banks have now pretty much "cut" their large prop desks. The reality is that all the risk is being taken on the so-called customer books. The large positions taken will be excused as "preparing for customer flow".
"There is a purpose to trading activity as opposed to long term investing, by the way, and that is liquidity"
Up to a point but the "pools of dark liquidity" and algorithmic trading in equities have not been shown to add liquidity but cause panic, as in the flash crash earlier this year. The systems are either designed to turn off when conditions get hairy or press on an already panicked market. Not very helpful, really.
""Speculation is a zero-sum game" is a nonsensical statement, sorry. As long as market goes up, all speculators win. When it goes down, all speculators lose. Therefore, it is not a zero-sum game"
Well, clearly wrong as some are short, as has already been pointed out. Also wrong, but less clearly, as when equities or bonds are revalued higher, it means the returns for people who HAVE to invest today (e.g pension funds with new money) by definition get lower returns. It is borrowing money from the future to pay MTM bonuses this year.