An abhorrent tone is one that regards the subject matter with hatred and disgust. It is different from both hatred and disgust in that it often invokes a visceral feeling of repulsion and presents the subject as being totally alien from and anathema to a commonly accepted reference point (eg. Democracy, the human race).
“[O]utside the ordered universe [is] that amorphous blight of nethermost confusion which blasphemes and bubbles at the center of all infinity—the boundless daemon sultan Azathoth, whose name no lips dare speak aloud, and who gnaws hungrily in inconceivable, unlighted chambers beyond time and space amidst the muffled, maddening beating of vile drums and the thin monotonous whine of accursed flutes.”
-- The Dream Quest of Unknown Kadath – HP Lovecraft