The main question for this argument that piracy does a lot of good is: are the people who are pirating things using it for this purpose? I don't think there's an ethical conflict for me to say that I am happy for piracy to exist for software that is otherwise unplayable, but think that piracy should not exist for new games that just come out.
Someone quoted a study that within the first 14 years is where most of the profitability comes from. Maybe I'd be okay with people pirating anything that's been around for 14 years, but I think most people who keep using this "pirating is good" line won't agree with this compromise.