I think the reason why it shouldn't be claimed as a moral good is pretty obvious - authors deserve to get paid for their work. I certainly can't claim I stand on a bedrock of morality as I've used it from time to time, but even though I don't have the money that a lot of HN commenters do I make sure to not use it for small-time authors. Even really successful authors I'll only use it about 50% of the time.
If you want information to be free? Great. But most of those authors wouldn't be putting the work in to making that information/literature in the first place if they know they aren't going to get paid.
If you want information to be free? Great. But most of those authors wouldn't be putting the work in to making that information/literature in the first place if they know they aren't going to get paid.