Agreed. What it comes down to is "YOU BETTER DO THINGS EXACTLY AS THE COMIC STATES OR ELSE IT'S A PIECE OF ****!!!!!" It's this kind of fanboy mentality that limits the potential of imagination and creativity.
Yeah, I agree with that too... and it's one of the reasons why I feel MOS was a good movie. Not a perfect movie, but so many of the complaints waged against it seem to be, "Superman would never do that! He would do this!" And it's like... the character has been around for over 75 years and if you really went through every single comic book appearance, you'd find a TON of inconsistencies. The Mark Waid Superman would never take a life under any circumstance, but the John Byrne Superman would. The pre-crisis Superman has an overabundance of self-confidence and never doubts himself; the post-crisis one is the opposite (this was even a major plot point of Infinite Crisis).
So while seeing this Superman questioning himself and humanity, being forced to reveal himself due to Zod's actions, making some rookie mistakes and ultimately being forced to kill might have rubbed some purists the wrong way, that doesn't necessarily mean these were bad choices. And it also doesn't mean that Snyder "didn't understand and/or care about Superman."