I love a friendly debate 😀:

The statement says How can you steal something that the customer cannot own?. You can definitely steal it if "you" aren't the customer. And you can steal it from a "customer" even if the customer doesn't own it and someone else does. And you can steal if even if you are the customer, because you aren't the owner. The only time you can't steal it is if you are the owner, because you own it.

The definition of "steal" you mention seems to be proving the point I'm making. Something can be stolen if the person stealing it isn't the owner, which is the case in the first three examples I mentioned above.

The statement is an odd play on words and loaded with assumptions that are left up to the reader, which is why it's super weird to use it to try to prove the point the author was trying to make.