My assumption is that the DK is just an empty animated armor. That's why he hates rats, they actually can get inside him.
Anyhow, it explains why he will not get rid of his armor: He is his armor. [/crackpot theory]
I'm not too sure he hates rats because they get inside him, he hates imps too and that'd just be plain wrong if one got inside his armour. It'd be pretty funny, but I really think the doctor in Act 1 is enough <img src="/ubbthreads/images/graemlins/shhh.gif" alt="" />
