I'm not pro-piracy but I think at the heart of piracy is the moral after-effect of corporations being able to produce too much demand.
It's like society's evolution towards more and more corporations creating apathetic but constantly product feeding consumers. At some point the adaptation process leans towards these individuals favoring a form of acquiring anything at a cheaper (preferably) free price because the opposite side of the spectrum - that of being thrifty, pragmatic, conservative...loses it's efficiency over time regardless if many still view themselves as conservative buyers.
One may make the counter-argument that this is over-thinking an age old practice of software piracy but in my honest opinion there's a huge difference between underground software "crack" sharing from wholesale piracy to mass consumer p2p usage.
Nonetheless just to support your topic:
Justification: Piracy helps promote businesses via consumer awareness
Rebuttal: Piracy helps promote BIG businesses. If piracy supporting people were truly for helping businesses, they would be a lot more intelligent in seeding certain products.
Instead the most seeded ones are often times also those that are mainstream. This doesn't mean the technology hasn't allowed for those who would seed or allow for a less costlier promotion of an item but... until piracy develops a seeder mentality rather than a leeching one, this justification won't ever reach reality. (and by seeder mentality, I don't mean just those who have the capability to possess seedboxes or seed 1:1 - I mean we have to have a conscious identity as consumers even if we're acquiring something that is cash free because it's not votefree. There are certain books or products that could help alleviate third world countries and then there are products that are merely entertainment junkfoods)