The point of Hacker News isn't "to discuss things that (insert whoever currently is complaining that the HN front page doesn't match what their list of most important links is) I think are important." It's to discuss what hackers find interesting. This is explicitly stated in the goal of the site. Hacker News isn't a democracy, there are other places on the internet to find that.
ADDENDUM: To those who counter that Hacker News has become such an important place in the internet consciousness that it needs to now address these things, consider that a primary reason it has become as important as it is now is that the rule you now complain about have done what they were intended to do.
Well, if we are going to truly embrace that premise, then I see little room to be upset. Discussions being flagged off is the HN system acting undemocratically to shape the discussion to its tastes.
The flamewar detection system isn't smacking down topics, it smacks down types of discussions. Certain topics seem to generate little but flamewar and get regularly smacked down, indicating to me that HN has little interest in (or perhaps more accurately, ability to) discuss[ing] those topics reasonably.
tl;dr: I agree, HN isn't for discussing everything. Far from not being okay with that, I think it is a good thing.
ADDENDUM: To those who counter that Hacker News has become such an important place in the internet consciousness that it needs to now address these things, consider that a primary reason it has become as important as it is now is that the rule you now complain about have done what they were intended to do.