While I was writing my post I was on the phone with a Schwab broker to confirm what I was talking about. The Schwab broker confirmed to me that an investor with a margin account/margin balance would have to have enough $$$ value in their account in order to short the stock in question. I had called a few months back about the same shorting question and that's what I was told.
Schwab has sent me a request a few times in the last year, offering to PAY me interest if I was willing to lend shares of something I owned to someone who wanted to borrow them to short the stock.
I told them to go F-themselves cause the interest paid was pittance to the potential gains those trying to take down a share price might get.
Plus its contrary to my best interest unless I was hoping for a cheaper price to add more shares at.