Looking at the examples of the leadership of men at the time Elrond made that statement what is there to disagree with? Theodin and Denethor are both sitting on their fanny's waiting for the end. Saruman and Sauron have both under their thumbs. Without the Hobbits to help Aragorn tip the balance where would men be?
Men were "scattered, divided, leaderless" because Aragorn's time had not yet come. Elrond certainly understood that in the book--Aragorn was waiting until it was time for him to move into his proper role.
I think the weakness in movie-Elrond's arrogant dismissal of Isildur was that he acted as though Isildur's inability to destroy the ring was due not to the ring's ability to corrupt the bearer, but due solely to man's inherent "weakness." If that's the case, then why not suggest an elf to do the job? The fact that Elrond not only didn't suggest an elf but in fact made it clear to Gandalf that Frodo should probably take the ring, makes Elrond's character a bit confusing and inconsistent. I don't exactly know why PJ decided to do this--whether he just wanted to introduce more conflict among the characters, or whether he needed a way to show Isildur being unable to throw the ring into the fire. Or perhaps there's another reason that will make more sense later on.