I suppose there must be a reason why we don't.
I suppose there must be a reason why we don't.
Because you're asking your portfolio manager to make you a custom index fund. The whole point of an index fund is to spread risk among lots of companies and sell fragments of that risk to lots of people. You can make your own custom index fund, it's called buying a share of every stock other than the ones you don't want.
You could short them to the same weighted percentage that they exist in the index but that's of course not completely simple and you have to pay fees for the shorted stock. If O&G had a convenient ETF (I don't know if there is or not, I imagine there is), you could short that rather than individual companies.
Shorting Facebook would be... interesting for your returns.