Sure but the open source part is mostly incidental to their work. They solve business needs for corporations.

That makes no sense at all. Software is not a scarce resource, unlike your money. If you donate money to a charity who gives it to Amazon, you would have good reason to be upset. But if you write a piece of software and Amazon uses it, other (needier) users benefit just as much!

Or to put it in another context, if you went and volunteered for a highway cleanup, would you get mad if Bezos drove on the highway you cleaned? Because that is what your position here is analogous to, and that seems like a poor line of reasoning to me.