Is "your thick skulls" and "stop saying stupid shit" unreasonable incivility when you're responding to someone who's telling you to shut up because he doesn't like what you're saying?
A quick review of my comments, including on this topic, shows it takes rather a lot to push me that far.
That Hacker News hosts "classic flamewar topics" is an issue in your court. E.g. in this domain, you could declare as non-germane any discussion of gun control per se, and limit discussions like this to e.g. the intersection of the 1st and 2nd Amendment issues these printed guns are prompting.
(Although I suppose it's hard to say "this makes gun control obsolete" comments are off-topic, but I have no dog in that hunt, it's not an interesting topic except in how it causes the authorities to over-react.)
The sign of a classic flamewar topic is that it ends in a recognizable meltdown end state, of which the-culture-war-will-lead-to-a-new-U.S.-civil-war is surely one.
Then it's a good thing I didn't say that, only pointed out that this topic in the US context is a part of our culture war. And it clearly is, e.g. given the severe political costs to his party, it's hard to see why Obama is still prosecuting it other than as part of a culture war.
(Seriously, I've just read a couple of stark statistics about the RKBA in the Age of Obama: 100 million guns have been sold (not all are new ones, but we bought enough to equip the active US Marine Corps on 2015 Black Friday (!)), and US firearms manufacturing is up 140% in units. I know people have been saying he's the best firearms salesman ever, but this was way beyond my gut feeling.)