Disable root graphical logins.
Period.
make it so gdm or kdm or xdm just exit.
hell, you could make the xinitrc script handle it:
if your uid is 0 then you throw up a hate-filled messaged and exit.
EOD.
If you can't flip to a console and take care of the problem there as
root, then you REALLY don't need to be logged into a graphical client to
do it.
Bite me !
I want to run some of my boxes as root with X, not to mention the
problems this would cause trying to work with some cluster setups and
embedded boxes. I have X code then even requires to run UID 0.
Users should have the power to choose, even if you personally think its
a poor choice.
If you have such a security fetish then go play with firewall rules in
the corner and leave us users to decide how to operate our machines !
Jon