Ah yes, the master Elf himself. Elrond was born way back in the early days of the First Age (or, put another way, is around a whopping 6500 years old during the events of the film).
Yeah, he's seen some things. And by "some things," we mean he's seen battle and death during the War of the Last Alliance and betrayal in its aftermath when Isildur failed to destroy the Ring in Mount Doom. So Elrond is a little jaded about the ability of men, but we can't exactly blame him.
As one of the oldest and most powerful elves left in Middle-earth, the bearer of an elven ring of power, and the leader of the Ñoldor elves of Rivendell, he carries a lot of weight on his shoulders. Elrond is the down-to-earth, pragmatic leader who knows how to get things (like throwing evil rings into volcanoes) done. If only he had given Isildur a little push back in the day but we imagine that would have led to a very awkward conversation with Isildur's troops gathered outside Mt. Doom.