If the movies have taught audiences anything, it's that fictional characters make a lot of dumb decisions - like, a ton of them. All the time. In most cases, this happens as a result of lazy screenwriting - filmmakers force characters to do things that they'd probably avoid doing in real life in order to move the plot forwards. Sometimes it's just easier that way, and who - really - is all that bothered about things like "realism"? Right?
But most movie-goers are bothered about realism, actually; it's what keep audiences immersed in a motion picture for the sum of two hours. And when characters start doing things that have audiences scratching their heads and saying things along the lines of "Why the heck did he even do that?" then you've got a serious problem on your hands. If a movie purports to embrace a sense of logic, it should make an effort to do so.
There are tons of movie franchises that skimp on the logic factor to such a degree that they've become famous for exactly that (Michael Bay's Transformers franchise, to name one infamous culprit). But there are other, more beloved franchises that constantly (and consistently) have their characters committing acts of narrative treason for the sake of a cool scene or a story beat or because the writers overlooked something by accident.
Franchises like X-Men.
Here, then, are20 idiotic decisions made by characters across the span of the X-Men films, all of which - when you properly think about it - showcases the series as one packed to the brim with stupid heroes who seem intent on making life difficult.