Of course I would. And everyone saying they wouldn't, in actuality probably would; if they really believed it would save the planet.
But most of us don't believe that. Personally, I don't think it's necessary for all humans to become vegetarians - but at the same time, we can't go on like this indefinitely. I'd rather see 3 billion people cut their meat consumption in half, than see 300 million people eliminate meat entirely. I'd also like to see standards for cruelty free farming put in place that all countries had to adhere to (which would drastically reduce meat consumption- there wouldn't be nearly as much to consume).