Consider HN is a hacker + entrepreneurial site you could see why people would not welcome Reddit/Digg support for piracy.

Being a hacker and a sometime entrepreneur doesn't mean that I have to think copyright makes sense. These are quite orthogonal to each other, and I would lose respect for someone if I found that they'd believed copyright invalid until they wanted to make a living off of it.

...I'm unclear why you are conflating support for piracy and Digg/Reddit.

I understand the attitudes of those so grossly offended by copyright and DMCA violations. But suggesting copyright infringement doesn't automatically disqualify an article from Hacker News.