[Iris Alantiel]

I'll have to agree with the people on this thread who are saying that Gandalf was just trying to get them to leave without getting shot, and specifically without getting the Ring Bearer shot. Gandalf was probably wise enough to see that however important his role in the quest might be, the really important thing was to protect Frodo as he carried the Ring to Mount Doom.

I don't know if calling them fools was really an allusion to "fool of a Took", although that's an interesting idea. But I think calling them fools was more a reaction to being worried in a tense moment - like if someone you care about has just had you worried to death, and then you find out they're okay, and you say, "You're the biggest jerk in the world, you scared the hell out of me!", even though what you really mean is "I love you and I would not want to see you harmed" (or shot through by orc arrows, as the case may be).

I'm really not too sure about this, b/c it's been a while since I've read it, but is there any evidence to suggest that Gandalf knew what was going to happen if he defeated the Balrog (i.e. that he would become Gandalf the White)? If so, perhaps "Fly, you fools" was his way of saying, "Contrary to appearances, I actually have everything under control, you just worry about not getting yourselves killed and it will all be okay." Of course, the Fellowship would not have understood the whole "everything under control" bit (I'm sure it didn't look 'under control' to them) but then that's typical Gandalf anyway.