The fact of the matter is that every citizen in the world could do all of the "green" things in their daily lives that they can and it would barely tick the needle on emissions down. The U.S. military itself is one of the worst polluters in the world.
A person's "carbon footprint" cannot extend all the way to the CO2 emitted when pouring the base of the factory that produces the gas in their car, in the same way that buying clothes at the GAP cannot condemn you for child slavery that the corporation benefits from.
You cannot put the onus for ethical business on the end consumer when the corporation pursues and benefits from unethical behavior, often times without the end consumer ever knowing about that behavior. It's ridiculous, and completely ignores the class element in the whole discussion.
This is a problem that must be solved from the top down, and corporate messaging to saddle the responsibility on the end user is disingenuous at best, incredibly maligned at worst.