I just watched this episode the other night, and I'm rather shocked at the things Worf can get away with! Successfully killing Duras, trying to kill Kurn...wow. At least Duras was armed and fighting, but Kurn wasn't. Sure, Kurn was suicidal in a socially acceptable way for Klingons, but still, it's amazing that Worf never seems to get more than a black mark on his service record for what he does.
Watching "Sons of Mogh" again just struck me with 24th century culture shock. Worf tries to kill his brother, fails, and doesn't get charged with murder, attempted murder, or any other crime. His colleagues don't even really blink an eye at it - the next wee they're back to work, no discomfort around him at all. I suppose it's a logical consequence of their culture and era, since the characters of DS9 are surrounded with so many other diverse cultures. It's not as though Klingons are the only people with ritual killing in their culture - the Vulcans condone fights to the death, at least, and if I recall correctly, suicide is acceptable in their culture.
Still, to work with someone who is capable of killing their own brother, or at least attempting to do so, would be unnerving to us now, I should think, but somehow not really uncomfortable to people (well, Starfleet officers) of the 24th century. What a change in humans.