The carnist claims eating meat is ok because it's all part of the "Circle of Life"
It's a made-up theme song for a Disney movie. The "circle of life" is in zero respectable biology or ethics textbooks.
Can I kill another person and claim "circle of life" as a defense? Can I claim that stealing is ok because of some imagined "cycle of ownership" where "you get things, you lose them, you give them away, someone else gets those things... you know: The cycle of ownership". Me stealing your car is part of this cycle. It's like the water cycle or the nitrogen cycle but for your stuff.
Carnism has huge ecological impacts and is the number one cause of global warming. To claim that this is just some part of a natural "circle of life" that gives you moral impunity to put frozen beef pucks in your shopping cart is an insult to intelligent discourse.