"Without S31's actions, Odo's attempt at the end would have amounted to nothing.
By praising Odo's actions as 'the way to do it' you indirectly praise S31's actions as 'the way to do it'. Denying this doesn't change it."
That's a bad premise. That's like saying the only way someone can be seen as to be a good guy is if there are people acting terribly, and therefore we should thank the horrible people for making us look good.
"So, you essentially want children's tales, to tell you cushy facts that blatantly contradict reality, just because reality is too inconvenient for your ivory tower, cushy philosophying?
BTW that was the greatest weakness for TNG. Annoying, when it was obvious that, from a real world perspective, the 'correct' choice was noting of the sort; in most other circumstances where it occured, it merely diluted the show with simplistic/unrealistic black/white with nothing in between - it was just like watching a cartoon for 6 years old."
Star Trek is beyond the current world, it's not likely that the morality and ethics of people in that society would be the same as you would find today. Just like the morality and ethics of our world are much different then the 1700s.
And it's not sugarcoating something to look for the best in people. Take "In the Pale Moonlight" for instance. While it was great dramatically, and it was interesting to see a different take on a problem it just didn't feel like Star Trek.
Why couldn't they have come together to fight against a common enemy without duplicity. It's just a simple matter of the writer's choosing which choice is the right choice.