The Golden Rule just needs a little more depth to be applied here. You have zero holy places, but if you had property, you'd want people to respect it. Therefore, you should respect other people's property.

I think it's very much condescending if you treat the immorality of piracy as a base assumption held by both parties. If you treat it simply as your own base assumption, that's fine. But treating it as a base assumption of the other side and then arguing against their behavior based on that qualifies in my book.