Because a NYT op-ed about how heartless Rand Paul is is not part of an interesting new phenomenon, or even interesting at all in a hacker sense. I feel like people upvoted it because they agree with it and feel strongly about the issue, but it's just partisan politics. Politicians say crazy things all the time and I enjoy being able to go to HN and NOT see politics plastered everywhere.
FWIW I posted it for the social commentary on the perception of the poor in the US. IMO the personal attack on Paul was a minor aspect, more of an inspiration to give commentary than a personal attack.
http://ycombinator.com/newsguidelines.html