Dunno, kinda thinking if we dared him that so straightforward he would end up looking like, uh, a fool for falling for it.

[And given Satan's circumstances Filbo sympathizes and therefore tries to dissuade from making him look bad, come on, Filbo, you were afraid of the guy until, like, two hours ago]

Maybe...use it to nudge it to the result we want, though? Something along the lines of daring him to have a handicap of some sort instead? Or give us a bit of an advantage?