That's certainly a valid argument if your ethical standards are such that it's okay to kill some but not many.
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.