See the War Handwavium Scoring System and read the bit about “distancing”. Moore shows us directly the effectiveness of Veidt’s plan. The bombers had been launced. War was coming. Veidt stopped it. The notion that this Pax Adrianica might fall apart is only hinted at indirectly as being a future possibility, and Moore stops the story before we can see it directly. Moore distances us from that part of the reality.

In the graphic novel, we see Rorshach torture several people and get the truth. At one point, Rorshach mentions in the graphic novel that he had to torture several people before getting some good information about some specific plot point. But Moore never shows us those torture scenes. We see several scenes, directly in the graphic novel, of torture working. The negative aspects of torturing innocent people, is only referred to indirectly, in dialogue, after the fact. Moore distances us from the negative.

With the kid at the newspaper finding Rorschach’s diary, the fact that Adrian’s plan to stop the nuclear war might possibly be thwarted is created as a possibility, but while we see Veidt actually stop the war, we are distanced from the potential failure.

Whether Moore choose to end the story where he did because he wanted to maintain Veidt’s effectiveness and maintain some sympathy, or whether he just felt that was a good place to end the story, doesn’t matter for the War Handwavium score. The scoring is based off of what is in the story, and the score takes into account how close or distant something is presented to the reader.

http://www.warhw.com/war-handwavium-scoring-system/

Not only did Veidt stop it, but Dr. Manhattan agrees after it happens that it’s the only course, that they must follow through and keep it a secret.

I think Moore might sympathize with Veidt the same way he sympathizes with V in “V for Vendetta”. But whether you as reader sympathize with him, what matters for the War Handwavium score is what we are shown directly versus what happens off screen, and how the world operates as shown by what is effective in that world. Torture, in Watchmen, is effective. Vigilantism is effective. Veidt is effective in stopping nuclear war.

That is how the world created in Watchmen works. Whether you sympathize with Rorshach or not, he tortures people and extracts useful information from them.

But his actions aren’t infallible, and he’s just a man. In the book (but not the movie), he asks Manhattan if he’s done the right thing in the end, as though he’s the hero of the story and brought it to its climax, and Manhattan simply tells him that nothing ever ends, which leaves him visibly shaken.

Furthermore, in the book, his descent into madness is mirrored in the “Tales of the Black Freighter” segments. The man in that story thinks he’s going to save his people from oncoming doom, but his journey wears down his soul until he’s a monster.

And really, it’s right there in his name: Ozymandias. “Look on my works, ye mighty, and despair,” written on a broken monument in the desert. Veidt believes he’s built a lasting peace, but the last page/scene shows “Pax Adrianica” on the verge of shattering to pieces at the hands of a common slob.