...and Duras (Yeah it was an act of vengeance but it was still murder).
Not murder, that is how Klingons handle their business. That's why they have the "Right of Vengeance" to begin with.
I think the above shows my biggest problem with TNG, especially in comparison to TOS. In TOS, it seemed like humans were out in the galaxy to explore and learn and many times learning things about themselves that didn't look very good when they stepped back and examined their attitudes and actions. In TNG, it seemed like the humans were out in the wilderness to teach the natives about truth, justice and the Federation way.