I think loqu's got it. (I admit this did confuse me at first until I read loqu's explanation.)
'Timent' appears to be intransitive.
It isn't: Servī malī dominum
timent. "-um" is the accusative of masculine nouns, so 'timent' is transitive. I think you're too fixated on the translation "be afraid of". If you think of it as "fear", as loqu suggested, everything falls into place. "The servants are afraid of the master" and "The servants fear the master" mean the same thing, right? So if "timēre" is "to fear", then "timērī" (passive infinitive of "timēre") is "to be feared by". Servī ā dominō nōn timentur: the servants are not feared by the master (= the master does not fear the servants). It makes perfect sense to me.