Here’s my logic:

Billionaires like Jeff Bezos exist because people buy from and support the billion-dollar company he runs. Therefore, by buying from Amazon, you are supporting the existence of billionaires like Jeff Bezos. To buy from Amazon, while proclaiming billionaires shouldn’t exist means supporting the existence of billionaires while simultaneously condemning their existence, which is hypocritical.

The things Amazon offers are for the most part non-essential (i.e. you wouldn’t die if you lost access to them) and there are certainly alternatives in online retailers, local shops, etc. that do not actively support the existence of billionaires in the same way Amazon does. Those who claim billionaires shouldn’t exist can live fully satiated lives without touching the company, so refusing to part ways with it is not a matter of necessity. If you are not willing to be inconvenienced for the sake of being consistent in your personal philosophy, why should anybody else take you seriously?