Question on Brandir.

[Maédhros]

From the Narn I Chîn Húrin

"Keep your hate!" said {Dorlas}[Darlas]. "It is as feeble as all your counsels. But for me the Orcs would have come and hung you as a scarecrow in your own garden. Take the name skulker to yourself!" And with that, being for his shame the readier to wrath, he aimed a blow at Brandir with his great fist, and so ended his life, before the look of amazement left his eyes: for Brandir drew his sword and hewed him his death-blow. Then for a moment he stood trembling, sickened by the blood; and cast¬ing down his sword he turned, and went on his way, bowed upon his crutch.

It seems to me at least that it was because Darlas attacked him first that Brandir killed him. It looks like a reaction and not something that he thought of.
IMO, if Darlas would have walked away, he would not have been killed by Brandir.