Walt Frazier, the great NY Knick guard, used to say that he knew he could steal the ball from the guy he was guarding at any time in the game, but he didn't, because he knew that if the game was close, he might HAVE to steal the ball.
Pressing the "moderates" to vote up or down on the filibuster MIGHT have broken the filibuster---or might not, and it might have pushed some of the "moderates" (for their own political survival in liberal states) to vote against it. By appearing "concilatory," they can get some props for their home elections and still have the option to vote against the filibuster if, after appearing "conciliatory," the Dems still screwed them.
How does one argue with that mindset? It could not have been stated more ardently by a liberal. I urge you to fight for your convictions. Adapt on!