Why do people in the green living section doubt that eating meat harms the environment?

These people supposedly care about the environment, but when I asked about being vegetarian for the sake of the environment, and linked the following article: http://www.taxmeat.com/ecological.asp I seemed to get negative responses.

Do they not believe that factory farming is one of the biggest polluters or do they just put their need for a cheeseburger ahead of their love for the environment? If they would cut down their meat intake, they could not only lower their environmental impact but would be living a much healthier lifestyle, cutting down costs of healthcare as well.

Producing just one hamburger uses enough fossil fuel to drive a small car 20 miles. By giving up the hamburgers, you could theoretically "pay" for the carbon costs of your drive to work.