In my experience it actually is more like the example/metaphor I used: People dont get mad at someone who is at their general skill-level and shows that, because that person made one mistake - specially if the person in question owns up to it, apologise and signals "It wont happen again, it was an honest mistake, I know what I'm doing" - like that DRK I had in a recent Tsuyu-farm-group: He placed his meteor to late, resulting in a wipe, but he acknowledge that, identified that he made the mistake (and why - he wanted to get one last hit in) and assured us it wouldnt happen again. And it didnt.
One the other hand I had people in such parties who wouldnt understand meteor-placement even after it was explained the third time - and yet they insisted on being in that content. Which is sort of their right, but its also the right of the 7 other people in the party to say "...yeah, not with us".
Most dismisses I'm seeing arent "pros" dismissing "pros" over one mistake - its "pros" dismissing high school players, who believe they're pros because they scored the winning goal against another highschool two seasons ago. Or in other words: Most people I see being dismissed are the ones who cleared the NM and believe because they managed that, they can clear the EX-mode just as easly and then fall flat on their face when they have to realise that EX actually requires an amount of skill and effort that they dont have (yet).
