There are three separate issues I see with this meta-question.
- The title of this meta-questions asks one question: can we derive claims from movies (or more generally, fiction)?
This is a duplicate question.
The consensus seems to be along the lines of 'only if writer expected a reasonable person to still believe it to be true, once the movie was over or the book finished.'
- The next issue is whether the hostage stand-off trope (arguably called a mexican standoff, arguably not) is actually such a claim. I haven't been convinced of this, which is why I haven't voted to reopen. Others may disagree; they are welcome to argue their case or vote to reopen.
The motivation for not shooting isn't necessarily clear; it may be more complex than has been suggested. Primarily are they worried about missing the shot, merely wounding the person or misfiring? Would they rather not kill the person at all? The fact that there is a whole TVTropes page for when they do start shooting suggests writers don't consider the standoff to be a pure one, and the claim is therefore weak.
- The final issue is that this question may or may not have been treated differently to others. This is the "Officer, why did you stop me for speeding, when you didn't stop everyone else?" gambit. The correct answer may be "The other questions should also be closed. Please flag them."