The idea that veganism is good for your health is a lie that many smart people have been duped by.

The animal suffering aspect is also problematic because animals in the wild suffer more than certain farm animals.

The GHG aspect is true though. https://twitter.com/karpathy/status/1278904720174673920

The "deforestation" aspect is also problematic because (1) the idea that earth needs more forests to breathe is a lie and (2) more forests = more animal suffering.

See this Brian Tomasik piece:

https://reducing-suffering.org/habitat-loss-not-preservation-generally-reduces-wild-animal-suffering/#Summary

There is also a problem with the reduction in GHG from veganism though; GHG emissions per dollar you spend are approximately constant. Money saved from not buying expensive meat gets spent on something else, which usually emits the same GHG or more than what the meat did.