Remus didn't yell often, but when he did Sirius listened. He was usually right. But he also couldn't completely give up this desperate hope that they could change something. Control something. Make someone's lives better, even if this version of him wouldn't live to see it.
"We have to do something though," he said softly, the desperation that had been simmering inside him since he arrived bubbling over. "Not just for us, but for Harry and everyone who died that didn't have to. Maybe we don't trust Dumbledore. But wouldn't it be better for everyone if the Dark Lord actually died in 81, instead of coming back later? How can we just let all those horrible things happen when we could fix them?"