Playing a bit of devil's advocate...
1. Shooting in self defense is, first and foremost, about hitting. You might call this Rule Zero; without the hit, the gun is nothing. Accordingly, one could argue from first principles that anything that detracts from the hit is contrary to the spirit of the thing in and of itself.
2. Most shooters will admit to shooting a gun with a short, relatively light trigger better than one with a long, relatively heavy trigger. Heck, if you watch most people with DA/SA guns, they don't even practice with them in double-action mode, especially when they want to show off how good they are.
3. Saying that trigger weight doesn't matter because of stress/short engagement distances/whatever is a flawed point of view. Stress magnifies shooter limitations, and under those circumstances you do not want a trigger system that complicates hitting the target with a heavy pull and inconsistent shot-over-shot trigger weights. Furthermore, assuming short engagement distances is to prepare for only the best-case scenario, which is misguided. Why would you want to handicap yourself in the event an other-than-short-range problem presents itself?
4. Consider the time factor. Deactivating the manual safety on a SA gun does not take extra time, because the action is done concurrent with the draw. With both guns on target in the same time, an accurate shot with a 12 pound trigger will take appreciably longer than an accurate shot with a 6 pound trigger... pulling a long 12 pound trigger cannot be done as quickly as a short 6 pound trigger without hopelessly duffing the shot. Trick revolver shooters with supertuned custom Smith & Wessons notwithstanding.
5. Everyone with a stake in fast, accurate shooting in competition uses a single-action trigger system when the rules allow it. Chalking this up to "tradition" requires that you not actually look at the guns involved, with their polymer frames and titanium parts and trick optics boosted from a MiG-27. Is there a reason why you wouldn't want to use a system noted for fast, accurate shooting in real life, too? (If not to the extreme of 2.5 pound triggers and holographic sights...)
(The real answer to all of this, by the way, would sound alot like: pick a system that works for you, and then master it.)