The UFP / StarFleet is tolerant of Klingon Cultural Practices & the option to kill on occaision.
If that means you have to eliminate a few dudes to crown the new Klingon Chancellor of the High Council (2x Mind You), they're more than happy to accept their ways.
Remember, it's the Vulcans who came up with the concept of the "
Vulcan Hello" for the Klingons after their own species disasterous encounter with the Klingons their first time.
Slug what now?
Blood Oath paints a different picture:
DAX: Kira shouldn't have told you.
SISKO: Kira is my First Officer.
DAX: I don't have to tell you what this oath meant to Curzon.
SISKO: Jadzia Dax took an oath too, when she joined Starfleet. You're subject to orders, Lieutenant.
DAX: Don't do it, Benjamin. Don't make me disobey a direct order.
SISKO: I never understood this. I mean, whatever else Curzon was, he did have a fundamental morality. He wouldn't condone murder any more than I would, and yet he swore to kill this Albino and now you plan to go out and kill in his name. What about the laws of the Federation?
DAX: The Klingons have their own set of laws. This is justice to them.
SISKO: And to you?
DAX: I've chosen to respect their codes of honour in this matter, yes.
SISKO: You really think you're capable of doing this?
DAX: I don't know. There's only one way to find out, isn't there.
SISKO: Let's say you are. Let's say you even survive this insanity. You expect to just come back here and resume your duties as though nothing's happened?
ETA:
Honestly, Picard was not so happy either:
PICARD: Mister Worf, your service aboard the Enterprise has been exemplary. Until now.
WORF: Sir, I have acted within the boundaries of Klingon law and tradition.
PICARD: The High Council would seem to agree. They consider the matter closed. I don't. Mister Worf, the Enterprise crew currently includes representatives from thirteen planets. They each have their individual beliefs and values and I respect them all. But they have all chosen to serve Starfleet. If anyone cannot perform his or her duty because of the demands of their society, they should resign. Do you wish to resign?
WORF: No, sir.
PICARD: I had hoped you would not throw away a promising career. I understand your loss, We all admired K'Ehleyr. A reprimand will appear on your record. Dismissed. Mister Worf, isn't it time for the truth about your father's innocence to be told? After all, you only accepted this dishonour to protect the name of Duras and hold the Empire together. Now that he has died in disgrace, what is gained by further silence?
WORF: Each member of the Klingon High Council has shared in that lie. They will not be so willing to admit their own dishonour. But the day will come when my brother and I will convince them to speak the truth.
~Reunion (TNG).