Stocks with a negative ß
A company with a ß of 1.000 has the same expected return rate as the risk free rate.
I therefore believe that CSB Nair is incorrect: if the expected earnings are just lower than the risk free rate, then the company has a ß between 0 and 1, but not negative.
Yet it is possible to imagine a company with a negative beta! This is (only) the case when its returns are counter-cyclical and move opposite to the market
Of course, the beta of most companies' stock is positive. But there are financial assets which are designed to have negative betas. For example, funds that engage exclusively in short-selling make money when the market is falling and lose when the market is rising. Including these assets in your portfolio decreases your volatility.