As a writer, I must say that this always makes me feel sad. If I complain about piracy, I get modded down. It's pretty clear to me that a few people with the power mod down any anti-piracy sentiment. I'm almost certainly going to get modded down now.
Many of the others have posted some good explanations that tie the pro-piracy people to the idea that information wants to be free. In other words, asking people to pay is somehow kind of equivalent to censorship.
It's worth noting that the pro-piracy vibe is only for pirating the work of writers, musicians or movie makers. Not pirating software. If someone suggests simply stealing someone else's code -- or even just ignoring an open source license -- people jump all over that person. The programmers stick together. But the artists are in another tribe so it's okay to rip them off.