Ironically, the speaker at the beginning of the chapter doesn't make a very strong case for accepting Ender in the program. He simply says, "I've watched through his eyes, I've listened through his ears, and I'm telling you he's the one. Or at least as close as we're going to get" (1). His case is completely personal, based on his own opinions and experience (with and without Ender), and immediacy seems to trump everything.
His short argument here actually tells us a few things though. First, it tells us that whoever this speaker is (at this point he is yet unnamed), he is as much at a loss for saving the world as anyone else. Second, it tells us that the search has come to a crucial point. If Ender is "as close as we're going to get," then the threat must be even greater for them to make the choice now. Finally, this tells us that the speaker knows Ender, right now, better than anyone else in charge. (This is of course thanks to the monitor.) In reality, this man (who is Graff) is actually primarily responsible, at this point, for "saving the world." It is a huge burden and one that he seems to take flippantly. Of course this is not the case, but in many ways, his tone is necessary for survival for everyone. The situation alone tells us that this man is under a lot of stress and pressure. It seems he uses humor to cope.