I mean - I guess you can, or at least I try to. The only problem is that people are nuanced, and IRL other people tend to react to what they see.
My Morzan is a pretty nasty combination of insanity (in the most literal sense, as he is severely damaged by his dragon's nulled name and Morzan's own refusal to ever let go of that broken mind) and nastiness (is pretty aggressive, violent, alcohol-depended, explosive and most importantly in complete refusal to accept anyone's help, which in return causes him to damage more and more people).
But I also try to make him a man with his own multifaceted personality. He is not nasty 24/7 for the sake of it because we need a bad guy.
Referring to Murtagh, it's not that he wanted to harm him. It was a bad moment due to his nameless dragon. Only after the fact came into play Morzan's deeply flawed personality, as he was angry that now Galbatorix was gonna be up his ass about what happened and so it's not that he didn't care about Murtagh. It's more than his problems with his dragon eat everything away, and the mess that in my fanon is the relationship between the Forsworn and Galbatorix comes close second after it and- fuck it, the child is alive and he wouldn't know what to do with him now anyway.
And, yeah. He is I guess insane and he is surely an asshole, but he is not an asshole because he is insane. At least, he could choose not to be.