I suggest that because farming plants also involves killing animals (using poison or mechanical means) and it is unreasonable to believe that someone who fails your ethical standard when raising animals for sale will take more care about rats/birds/… when raising plants for sale.
More generally, you'll always be able to whatabout vegans, because to live is to kill --- it's completely impossible to live in modern society and not harm something somehow. I feel that I'm obligated to do the best I can under the circumstances.
[0] https://www.surgeactivism.org/articles/debunked-do-vegans-ki...
My standards for how to treat animals don't depend on whether I eat that animal after it's died. "Can maltreat as long as I don't eat it" is IMO difficult to justify.
You'll note the wiggle room. It's not about being perfect and never contributing to animal harm because that's impossible. It's about doing the best you can in a bad situation.