You both have good points. One interesting aspect is that this volunteer labor is actually contributing to what is making the product valuable in the first place.
You could volunteer to do QA for a software company, or volunteer to clean the floors at a bank, or volunteer to work on an assembly line… And we’d likely criticize those businesses for taking advantage of that labour if it were systemic and widespread.
On the other hand you have open source projects which are freely licensed for huge corporations to make tons of profit from, and all we expect is that they give something back (but we don’t even hold them to that).
It’s interesting to think about where moderation work sits among these.