To be fair, I've heard more than a few writers, directors, and actor state the best villain doesn't know they're a villain.
Possibly. Think of that bit in Gladiator when Commodus (villain) is comparing himself to Maximus (hero); he says 'you take life when you have to, as I do'...he genuinely believes the various murders he's carried out or ordered are good, or at least necessary for some kind of good purpose. But to us as viewers, it's obvious what he's really like - he doesn't take life when he has to like Maximus does, he takes life when he feels like it - he didn't have to kill his dad, he didn't have to have Maximus's family killed, he didn't have to have those mistaken guards killed. All of those only happened because he wanted them to. Of course, whether he knows these actions are wrong and is trying to justify them to himself, or whether he genuinely believes they were the right things to do is totally ambiguous.
On the other hand you have characters like Darth Vader and MacBeth who are obviously bad and they know it, but they do it anyway simply because it's what they want. Selfish, really, rather than deluded.
They may be aware of the fact they commit villainous acts, but in their mind, anything they do is justified by a higher (even noble) purpose or goal they have.
Makes me wonder how Hitler considered his actions; did he genuinely believe the invasions and massacres he ordered were for a greater good?
TLC has clearly cast them as rational, somewhat barbarous, greedy beings. Certainly a pretty big character flaw for an entire race, but if anything, it makes them more pathetic than evil.
I must disagree a bit here. Read the Lego Shop's description for the Troll Assault Wagon:
The evil trolls are on the march with their powerful assault wagon! Can the heroic knights stop the giant troll and keep the massive cannon from being fired? You decide!
The dwarves kingdom is under attack by evil troll warriors! It’s up to the clever dwarves to fight back with their mining battle-wagon, equipped with triple spinning blades and a powerful catapult.
TLC seems to have decided on a simple black and white 'us vs them' mentality; the trolls are evil and must be defeated by the heroic and clever humans/dwarves.