Well, I like meat. And I'm an environmentalist. Cows (the main producer of greenhouse gases) will continue to produce gases even if fewer people eat tham, because the cows won't magically die off and the farmers won't stop producing because someone somewhere will eat meat. Man has eaten meat since the beginning of our time, and that's not likely to change anytime soon. More greenhouse gases are produced by decaying insects than by humans; should we ban bugs?
I recently learned that CO2 stays in the atmosphere for 100 years. That means that we are currently dealing with the gases produced in the early 20th century, when standards were a lot less strict. I believe the United States has done as much as it can do with current technology and attitudes. The UN and other organizations need to spend less time bashing America and more time getting China, Russia, and Indonesia to start cleaning up their industries. Until you develop a global solution to greenhouse hases one country could reduce all it wanted to but another country's emissions would fill that void. If people just paid a bit more attention to the world around them, rather than their insular lives, then everyone would be better off for so many reasons.