I think the only thing that should ultimately matter to the developers is whether they’re losing sales from people watching “Let’s plays” or gaining. From what I consistently see, when popular Youtubers play indie games that would otherwise go overlooked, they increase sales by quite a bit.
The Developer is making a…

The way he talks, it’s as though he’s trying to claim that he makes it all his own work when 90% of his content was created by others...

It’s his art medium.