Yes, theoretically correct, for every seller there has to be a buyer. However, for all practical purposes, a trader is not always a seller. If a trader were to short all across the board, he would not be a great trader. He would be a great gambler who puts everything in one basket without hedging his bets. A trader does not always pick the right stock at the right time to short or to long.
Do you know of any “great” trader who made out like a bandit in a bear market? Anyone can get lucky some of the times, but to be great, you’ll have to be lucky most of the time over the long haul. I think that’s what differentiates the real great baseball heroes from the mass.
Thanks.