I'll try to tackle the contrary arguments one at a time.
A Corpse is a Creature
This seems pretty clear to me. Speak with Dead wouldn't work on it otherwise, since it very clearly targets One Dead Creature. No creature, no speaking. This is backed up by Raise Dead, and thus all the resurrection spells as well. I don't know where people got the notion that a corpse is not a creature.
It Has Intent
I'd originally intended this to say, "there is a lack of evidence that a corpse has no intent." The fact that answers must be "brief, cryptic, or repetitive," does not indicate that there is no will behind the answers. I would argue it only indicates that the one answering is unable to form or hold onto the complex thoughts required to string comprehensive sentences together. It only has a cheap semblance of life, after all.
If successful, the corpse can refuse to answer your questions or attempt to deceive you, using Bluff.
This, though, indicates will. The contrary interpretation ("[this means] that, mechanically, Bluff vs. Sense Motive is how you determine whether inaccurate information is so.") makes no sense. According to the spell, the corpse (sorry, dead creature) can, if successful, willfully remain silent or give false information in an attempt to mislead you.
Further, without intent, how could there be a distinction between dead enemy creatures and dead friendly creatures?
This Still Might Not Help Fred/Bob
A corpse, under the effects of Speak with Dead and Zone of Truth, cannot deceive you. There's no reason why it cannot refuse to answer, however; this is where Fred/Bob could get frustrated, because if the corpse refuses to answer I can't imagine there are a lot of options for him to convince it otherwise.