Although the repetition in "dviṣaṃ dviṣam" might suggest that the author had the gerund in mind, there are two problems.  One is the morphological expectation that the first syllable in such forms will always be heavy, which for a root with a short vowel followed by a single consonant is regularly achieved by guna strengthening: dveṣaṃ dveṣam.  The second is the syntactical expectation that the agent of the gerund will be the same as the agent of the main verb, namely the physician rather than the patient.

It might be better to take this as the accusative of the nominal form dviṣ.  Then I suppose the repetition might still express repeated or habitual behavior, as reflected in Dominik's translation (rather than being distributive, referring to a hater of both physicians and kings).  This raises the further question, though, of whether it refers as an adjective simply to a patient who is hostile (in behavior or personality), or as a substantive to one who is (politically or professionally?) an opponent.

Yours,
Gary.

Gary Tubb, Professor
Department of South Asian Languages and Civilizations
The University of Chicago