Reading your comment again, I can see that I have slightly misinterpreted/misrepresented it.
It still seems though, even if you were being more nuanced than I'd credited, that you seem to be saying you would rather he made a film delivering a different message to the one that he did. It seems to me that you are still effectively criticising the director for not presenting the debate which you would like to have been presented.
Isn't it a case of waiting for that particular film to come along, and in the mean time assess A Short Film About Killing for what it is? rather than for what it isn't or what else it might have been?
A lot of films say something, or make the attempt, they take a position, but that doesn't give them a free pass. Well, he meant to do this, so we can't criticize it. No, we criticize movies because we feel they fail to do this or that all the time, even great movies and directors - and something in the delivery didn't gel. I felt the approach here, the message, which was very important to director, was delivered with a heavy hand... that a subtler, more nuanced approach might have made for a better picture. I am judging the movie for what it is, and I found it lacking. It's not the position, it's the telling, which felt forced to me.
Now, you can get away with that sometimes... I'm not really in line with Mrinal Sen's politics for example, but I love how he tells a story, how he relays the message. I thought Chorus, for example, was amazing filmmaking, even though he's repeatedly hitting his audience over the head with a big Marxist hammer. I think the politics in Soy Cuba are the same - big hammer propaganda, but it's so gorgeously filmed and such a powerfully told picture, that I'm absolutely enthralled with it. And I go along with it not because I agree or disagree with its position, but because on cinematic terms, it's astonishing.
But I feel Kieslowski stumbles in his telling, most especially as a stand-alone. Certainly, you can take a humanistic approach about a horrible act, Dostoevsky did so with Crime and Punishment, where even this murderer receives grace - even if he doesn't deserve it, and he knows he doesn't deserve it, he receives it, in the form of Sonja, who represents that Christ like grace and forgiveness.