Every time an incident like this happens, Hacker News squares off into its pro and anti-gun camps and has the same futile charade of a "discussion." At some point we have to concede these threads are mostly only useful for catharsis and political sniping, nothing we say or do here is going to have any real effect.
While you're perfectly right, the same argument can be made about just any discussion, be it Java code formatting or enterprise agile implementation... Discussions are useful for those who can get something from them, and can be ignored by the rest.
