I think what he means is by charging really low, or working for free, you're making it harder for those who compose for a living because they either have to charge less themselves, or face losing work. It's gradually making it less viable to be a "working composer". It's not that composers just care about money, but we gotta eat. We gotta survive.
So I think the argument is more aimed at the hobbyists who have a primary income from elsewhere, who compose for cheap or for free, and who make it harder for the working composer who composes as their sole income. It's not that we don't love making music, or that all we see is dollar signs. We're just in a situation where we rely on this for our living, and it's hard when other people do our job for free.
As a side note, it doesn't bother me when a developer tells me they can't pay me for my work (i.e. they don't have the budget). It does bother me when a developer can pay me for my work (i.e. they clearly have the budget), but doesn't feel like they should. I feel like developers are more and more encouraged by the oversaturation of free and low-cost composers to not feel like they should have to pay for music. And I think that is what is watering down the quality and integrity of music, because most indie games simply go with the cheapest option.
It seems like the "middle class" professional composer is slowly going extinct. Either you're a big-name composer who has enough clout to make a living working on high profile AAA titles, or you're working a day job and composing on the side for little to no money. No room for the guy who just wants to make a modest living doing what he loves.