If I discovered that HN moderators were banning links to specific major news articles they didn't like, I'd find that extremely concerning. As far as I know, the HN moderators restrict only comments which are needlessly inflammatory and posts which don't have to do with the technology industry, and I'd be fine with it if Twitter or Facebook adopted similarly general policies. (I'd be a huge fan of forming some version or corner of Twitter without politics at all, frankly.)