Advocates, regardless of ideology, tend to overlook junk science they like and focus their skepticisms on data that reinforces their beliefs. Nothing typifies that better than claims that eating meat is implicated in global warming to any great extent. No surprise, in 2006 the UN Food and Agriculture Organization repeated spurious claims that eating meat was responsible for more CO2 emissions than the entire worldwide transportation sector.
Part of that is bad science and some of it with even worse math (see Strange Climate Math - Driving Is Better For Pollution Than Walking) but rational minds are continuing to study the issue because all sources of emissions are important to resolving climate change.
In TIME, an interview with Simon Fairlie by Tara Kelly says just the opposite - livestock are not only not a net loss for the overall environment, they are a big gain.
