I despise Worf.
IMO the guy is a murderer twice over and has no place in Starfleet.
Would Riker have gotten away with beaming over to a Klingon ship and killing a guy with a sword,no matter the provocation?
Would Sisko or O'Brien get away with that whole blood transfusion fiasco?
And please,that "alien culture/outlook" argument is the most morally bankrupt horse hockey I've ever heard.
1. He was a subject of the Klingon Empire, killing a Klingon on a Klingon ship according to Klingon laws.
Worf obviously can't go around killing other people who aren't Klingons and don't accept Klingon rules and traditions, but that doesn't apply to another Klingon who does accept them.
What do you think humans should do, try to force their own morality on the rest of the universe?
Even though Worf is also - I presume - Federation citizen, his action is not a crime by Klingon laws, so I don't see how or why he would be prosecuted in a Federation court.
Now, Worf is also a Starleet officer, so they could throw him out, sending a message that a Starfleet member from a non-Federation world must only respect Federation laws, but obviously they didn't think that Starfleet should adopt this attitude.
2. I don't think that Starfleet has any right to force ANYONE to give their blood against their will. Having the right to make decisions about one's own body is a basic human right, which I presume still exists in Earth at least, if not in Federation at large. Nobody could or should have the right to force O'Brien or Sisko to give their blood against their will. I'm pretty sure that would be illegal in most countries today.
I'm not the biggest fan of Worf, BTW, but that's because he can be so annoying with his talk about Honor. But the two stories above were among his most interesting moments, which made him an interesting on TNG because he wasn't as bland, perfectly nice and PC as the rest of them.