Monopoly is not a synonym for "bad for consumers" or "company that should be broken up". Using it this way only confuses the issue.

I think it is more productive to advocate for a point in plain english.

Why argue that:

1) The existing definition of a monopoly is wrong

2) Your definition is right

3) companies that meet your definition should be broken up

4) Amazon is a monopoly by your new definition

5) Therefore, Amazon should be broken up

When you could just say:

1) Amazon is too big and bad for consumers