The claim here is that one can add up other things to make an even greater total
Everyone going vegan would cut climate emissions by 29%. The counterargument that carnists put forth is that "Well if you add up transportation of everything from humans themselves to textiles to sheet metal, you end up with a larger number". First, animal agriculture makes up a significant portion of transportation, including food imports, the majority of which are animal products. But whatever, let's ignore all that.
Imagine this scenario: consider what it would mean if 29% of greenhouse gas emissions could be attributed specifically to your favorite TV show called "Throwing Baby Kittens into Meat Grinders", and that we could lower greenhouse gas emissions by 29% just by stopping the production of this TV show? Would it be fair to say "Well, yeah but add up my driving, and that all together along with anything I've ever bought in a store ever (including my using clothes, computers, appliances, office supplies, etc.), and the movement of any product ever needed to deliver any service (from the metal that makes the cell towers to the wood that makes up my house). All of that added together makes up more greenhouse gas emissions than my this show!"
Obviously, you can add up together the emissions of a bunch of products and services and give them a single label. "Industry". "Transportation". Those each are huge arrays of services and products you use. "Agriculture" in any pie chart of emissions, to within a rounding error, represents only products involving cruelty towards animals for your entertainment.
What if it was the number two cause of climate change, would that change the fact that you could cut your footprint by 29% by eliminating animal cruelty from your life by making very easy choices? It's not even a reasonable position if it's right.