Piracy is illegal and unethical. You are stealing the property of the rightful owners of the content when you pirate. Yes, copying IS theft - you are depriving the owner of the content from having you not having the content. If the only way to preserve something is to pirate it, then the ethical and legal action is to let it disappear. You do not have the right to choose what happens with movies, music, etc., only the rightful owner can do that.
Combating piracy requires enormous resources on the part of the IP owners, which is taken from budgets that could be otherwise allocated to creating more art. When you pirate, you are stealing not just from the rightful owner, you are stealing from all of society by depriving us of art that would have been created if money didn't have to be spent fighting piracy!