You don't, though, which is the other person's point. Unless you've radically changed your consumption habits to only buy directly from producers (and ecommerce is ruled out, since you're not okay with the typical conditions of logistics employment). In reality, you've singled out Amazon. Which is fine! But at least admit that. It's a political statement, you haven't achieved labor rights veganism.
You also seem to be applying black-and-white thinking to problems of right and wrong. Some things are more wrong than others.
On a scale from "single mother cheating on her taxes so she can feed her kids" to "cold-blooded murder," Amazon is (in my opinion) beating puppies with sticks. When someone does something not just wrong, but inexcusable, and is unapologetic, I don't say to myself, "well, lots of other people have done/do bad things." I doubt you do either.