Personally, I don't think piracy can ever be completely justified and I find it slightly annoying when people try to. You may claim to have all these noble reasons why you are doing it, but the real reason is simply that you want something without having to pay for it (and if you really want to claim that's not the reason you're doing it, donate the money you would have paid for it to a charity, then I'll believe you).
However that doesn't mean I'm completely and utterly against it. I personlly think it's acceptable to pirate something that is no longer in production and literally only available from sites like eBay for a ridiculous price (for example, any PS1 game that is being sold for £50 or above). I also think it's acceptable to pirate something if you legitimately own a copy and want a back-up.
BTW, I have nothing at all against people who do pirate for other reason. If you want to pirate something, fine, but don't try to justify it to yourself and other, especially by claiming you're only doing it as some sort of moral stance against the company who made it (for example, a common excuse I've seen for pirating games is the amount of DLC and day 1 DLC in particular) because that's BS and you know it. You're doing it because you don't want to pay for it (again, give to charity and prove me wrong). Also, people need to stop with the whole 'I wasn't going to buy it anyway, they haven't lost a sale therefore it's justified' argument because that's BS as well. If you weren't planning on buying it then there would be no reason to pirate it since you have no interest in it. What you're actually saying is that you just don't want to pay for it, which simply isn't a justification for piracy.