You guys seem to be going out of your way to come up with reasons why Data had no choice to be a murderer.
Well, yeah. Like I said, you have to meet the episode half-way. At the heart of all this is a simple logical inference: If Data could have avoided firing, he would have. But Data fired. Therefore Data could not have avoided firing.
Now there are things that simply stretch one's tolerance and past a certain point it gets subjective. If you won't go along with the episode's intentions far enough to accept 'The Most Toys', well, fair enough. But if I were applying criteria as rigorous as yours, I'd have to reject all of Trek. Every species with access to FTL travel has Death Star style planet-killing technology, but war is still chiefly fought on board ships, often in neutral ground. Please. But depicting that realistically would mean they wouldn't be able to tell the kind of stories they want to tell. So they don't depict it realistically.
(Shrug) I'll take it.