well and in my opinion, to loathe indeed is to hate consciously, and this you can only do if you know what is hate, and this you can achieve firstly by perceiving what is love, an adverse form of hate. orcs couldn't; all their hate was in fact not theirs, but Morgoth's: he directed their minds and forced them to hate..thus i suppose orcs didn't possess a true ability of loathing [except, perhaps, that they hated Morgoth as well]
and it was Melkor himself who hated mowt of all: being one of the Ainur, and a Vala, he knew what is beauty and what is maybe love and pity of Iluvatar, and unable to make, he started to mock things..
and if we talk about other races, then maybe Men. i'm not sure but I suppose it was said that they somehow fell under the will of Morgoth, and even when he was thrust into the Void and all, the seed of hate stayed in them. they really have little pity and are quick to become enemies. like in 'Of Turin':the elves of Doriath only pity for Turin and forgive him the many slayings, and Turin himself slayes the other men whenever he falls into quick anger..
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