Livestock emissions are not a closed cycle in terms of heat. The methane produced by livestock is much more potent of a greenhouse gas than the CO2 captured by the plants grown for livestock. This might not be a big deal normally, but seeing as how we're maintaining at least 500x the normal cow population, it's a big deal now.

Fun fact, methane traps so much more heat than CO2, we'd actually be better off burning methane rather than releasing it directly. That's probably not a viable option for livestock, so it seems like reducing livestock is the most viable thing to do.

Agreed that fossil fuels are also an issue.