I don't think it is only what Nightblood perceives to be evil, though. You'll note that someone good will feel sick around Nightblood. These aren't people Nightblood perceives to be good, they are good. In addition to that, Nightblood doesn't just consume evil Investiture, or Investiture used for that wrong purpose. He consumes any Investiture.
Interesting point, Comatose. I think they also fit Odium, but as little as we know of Odium, that's really speculation. Does fit Ruin nicely, though. I see what you mean about the brokenness of Adonalsium. That could be the case, but it seems even less of a possibility, especially since that still would mean it's what Nighblood perceives. I wonder if he's Cosmere-aware.
In response to the issue that it's due to his nature as a Type IV BioChromatic Entity, I would point to Shardblades. Admittedly, they are quite different, but Sanderson has said that Nightblood is like a twisted Shardblade. They're the same thing, with different commands.