"I wonder if Mr. Big Mouth will stipulate that if Muslim leaders do condemn the slaughter of children, that Islam is just as sound and moral as, say, Christianity. He can read them himself, as can you."

I would say that Islam is just as sound as Christianity before this condemnation. But I think is a good idea for muslim leaders to step up and publicly state their views in this matter.
All the terrorists are not going stop murdering because a few Muslim leaders make these statements, but it will have a significant effect. The more muslim leaders who say this, the better.
The media should realize the significant of these types of statements. And there is the fact the media obessive interest in such creatures as OBL and lack of interest in real muslim leaders POV has resulted in the promotion of terrorists.

And failing to make such statements results in harming Islam.
The consequence of 29 terrorists flying a plane into buildings and killing 3000 people is that two nations of 50 million were liberated and set on a path which could lead to much brighter future. And America and the world has become stronger.
In the same way these acts of terror can strenghten Islam. Here is an opportunity for Muslims to fight evil. Defeating terrorists will require and will reveal truth- it's a perfect opportunity to teach true Islam.

Even if the muslims clerics are like George Carlin's cynical Cardinal in the movie "Dogma" [who's only concern is increasing the "market share" of Catholics] denouncing acts of Islamic terrorists is "good for business".