The most dangerous people throughout history take morality very seriously. They have so much commitment to their moral system that they're willing to kill millions of people to enforce it.

People like Andreessen are not without morality. Their moral system is right-libertarianism.

The people I am least afraid of are those who are without a deep fixation on morality.

The person you're replying to was talking about "virtue", which I'd argue is an entirely different thing than "morality". Virtues are traits that can help people be better humans, while morals are rules separating right and wrong. Things like courage, patience, introspection, kindness, etc, are all virtues, while morals tend to be much more of the Ten Commandments variety.

I don't think anyone has ever killed people or gone to war for a virtue, but they certainly have to enforce their moral code on others. Probably the worst combination is people with strong moral beliefs but few virtues, since their lack of virtue both fails to temper their moral fury and poorly guides the moral determinations they get so fired up about.

I think there's a Goldilocks zone of moral flexibility and openness somewhere in between complete moral rigidness and total amorality, I think.

The zone of moral rigidness contains all those species of fundamentalism that have caused so much conflict and atrocity. It's one one of the very bad zones.

But another very bad zone is the total amorality of psychopaths and narcissists (and they often pretend to be in the other zones), and they are also responsible for so much destruction an atrocity.