You're kidding right? The guy who had one of his own generals executed using a 14.5mm anti-aircraft gun? The guy who had his uncle torn apart by vicious dogs? Their is nothing liberal about him and he is rational only so far as being a functioning psychopath (I guess that's the evil dictator part you're talking about, but I think you're being too kind).
The Japanese were told not to surrender, during WW2, to Americans because we were cannibals. There's political leverage in dehumanizing your enemies. The has been no such confirmation of Kim's execution methods. Of the examples you mentioned, one has been deemed a hoax, and the other a rumor. A number of N. Koreans have made been made famous by "exposing" the regime, and have then subsequently found out to be lying.
Now, I'm not pinning angel wings on Kim nor am I saying that he hasn't committed the atrocities that he has been rumored. What I am saying, is that when you hate, or fear someone, it's easy to believe the more outlandish things.