You should stop casting these guys as villains, it obscures the main point of your argument. You would probably do the same lobbying if you were in their position. (Rather, if you were a major shareholder in Exxon, you would demand that managers do it.)

Just think of this in terms of Exxon &c having an effective negotiating position for blocking the carbon tax. We don't have to buy things at current market prices, but at a discount. Recognizing that there's room for negotiation is what everyone overlooks.