It's hard to comment on this post considering how many times we've seen the "HN-is-dying" meme, but for me this time it really resonates.
What has made HN interesting is the fact that it was boring to the vast majority of people on this planet. The topics were generally speaking on a very specific set of subjects that you largely had to be in the technology world (and of a certain technical disposition) to relate to.
The relative boringness of these topics led to comments by folks who found them particularly fascinating, setting a high community standard and discouraging soapboxing (comparatively speaking, of course -- I'm under no illusions that HN was ever the most pristine and idealistic place). For a long time I thought PG did a good job of enforcing that culture by shutting down off-topic conversations and keeping the focus fairly intense.
The problem with political posts is that they are often extremely relevant to hackers, especially these days. But everyone finds politics interesting, and everyone (myself included) believes their political beliefs are equally valid. Watching snarky posts and soapboxes get rewarded does send a message that this is how to get noticed. Long-term, I fear this fundamentally coarsens the level of discourse by making it easier to dismiss the beliefs of others and making it easier to participate in situations where I feel ignorant.
Unfortunately, I think there's only one way I know of to stop this -- which would be for PG and/or the moderators to take an active role in enforcing the "no politics" rule that's already in the guidelines. But I think they're perhaps legitimately concerned about censorship -- anathema to hackers -- and have kept a loose hand. Beyond that I'm not sure what they can do.