Why the "But China and India!" excuse doesn't work on global warming regulation -- demonstrated using pies

This WaPo discussion brought up a pet peeve of mine:

Clifton, Va.: So does anyone in the WH have the courage to tell the American public that no matter how much they sacrifice and lower their standard of living to fight global warming that it will not matter one bit. If India and China aren't going to do anything why should Americans pay more for everything, stop grilling outdoors, not use their fireplaces and pay more for everything.

Scott Wilson: That does make it a tough sell, but we'll see what emerges from the Copenhagen conference later this year. The United States and China are about neck and neck at the moment for title of world's biggest polluters, so the Obama administration would argue that a)the U.S. reducing its carbon footprint is essential to begin taking on climate change regardless of what others do, and, b) that doing so will allow the U.S. to better lead by example by removing some of the hypocrisy from its message. And, yes, it will likely cost more.

For me to illustrate why the guy from Clifton, Virginia's argument is wrong -- and I'm not touching the bit on China and India doing nothing, because that's not true, and it will be increasingly untrue if we start competing in good, green jobs -- let me use a thought experiment.

Let's say you had three guys. Guy A, Guy B, and Guy C. Guys A-C like to throw pies at people.

Guy A gets up every morning and goes out and hits 50 people with pies (he's very prolific). Guys B and C throw 25 pies each day. That adds up to 100 pies a day!

Let's say Guy A decided one day that he'd cut his pies down to 25 pies, just like Guys B and C, but that guys B and C decided they wouldn't reduce (pie) emissions at all. Even though they didn't reduce, Guy A, as the chief pie emitter, still would've cut the pie emissions overall by 25% just by reducing himself. Lots less pie on the face, no?

The point here is this: if the Chinese and Indians aren't taking bold steps on global warming, that doesn't mean we shoudn't. As a huge polluter, we can still make a massive impact by reducing our emissions, especially in the short term while our economy is still quite larger than that of India and China. If we just keep emitting and India and China continue to grow, it's even worse. So, no, it's not ideal. But it's a start. And that makes a big difference in cases like this.