Well, no. But you're also not really taking anyone's livelihood away if you choose to not sell some item in your shop. It's the "de facto monopoly" that's key

Well, no. But you're also not really taking anyone's livelihood away if you choose to not sell some item in your shop. It's the "de facto monopoly" that's key here; practically speaking the situation is "deal with corp X or bust", and avoiding these companies is typically an enormous uphill battle, or even border-line impossible in some cases.