No idea, but it looks like you're not getting man-db anytime soon

Given that man-db wants to also pull these:
bsdmainutils bsdutils coreutils debianutils groff-base mktemp

you could try simulating installation of each one individually, e.g.
# apt-get -s install bsdmainutils
# apt-get -s install bsdutils
..

and see which one(s) cause the whole mess.

Honestly, if all you want the man *database* (without the man program, etc.) I cannot imagine how the maintainer managed to massively fvck up the dependencies (but hey, this is debian).

One option is to simply unpack the .deb and live with it..