Yeah I'm pretty sure if I'd just killed a bunch of people in a fit of rage after a lifetime of being a peaceful person, I wouldn't be like: "Oh yeah guys, I just killed a bunch of people...so am I a bastard or what?"
You can feel guilt without wanting external judgements from strangers. That's the natural reaction, actually.
Kevin was essentially trying to hide behind the illusion of normalacy because he felt shame and guilt. Two things that an 'Eviiiiiiiil' person would not feel. It's true he tried to block Troi and caused a problem there, it's obvious he was still in an emotional state of semi-shock/denial. Certainly that is natural.
I'm not excusing what he did, and Kevin doesn't expect forgiveness, but none of his motivations or mistakes were unreasonable or unusual. They were just on a bigger scale.
Screwing with Troi's head noes not = evil. Or sexist.