You still don't get the point why we started talking about psychopaths. The point is this: their behaviour is morally bad yet can be perfectly justified on the rational ground.
All this is to prove the point that morality cannot be derived from rationality. Even worse, moral acts which receive the most admiration are completely irrational.
To give a simple example: if I find a wallet in the street the moral thing to do is to try to find the owner and return it to him. Yet the rational thing to do is to keep the wallet and spend the money.
Unless you can to prove that being egoistic in this case is irrational. Good luck with that! It's morally bad but not irrational.
Their behavior can be wise and rational or unwise and rational. To be wise is to take a long term view of your own future when deciding on a behavior. If you take a short term view, similar as with investments, you're pretty much gambling. When you gamble you might gamble based on some rational theory but you typically lose long term and this is what happens a lot of the time with psychopaths who as I said have great difficulty taking a long term view.
A narcissist who follows a wise strategy can be perceived at one of the most moral people in society whilst also being completely rational and selfish. Narcissists can manage this because narcissists care a lot about how other people perceive them and this is a key difference which in my opinion is the real thinking behind moral behavior. The moral behavior is something an individual adopts in order to be perceived a certain way by others in society whom they respect or seek the respect of. So it's actually rational behavior to adopt moral behavior but only if you take a long term view and think long term.
I don't have to do that. I can show you that you can be rational but have a short time horizon or you can be rational and have a long time horizon. If you don't believe you are going to live more than 5-10 more years you might not have any reason to care about social conventions of society or adopt the moral norms of your community. But if you do intend to live beyond 10 more years and you intend to stay in that community, then it becomes rational to adopt the moral norms of that community. There is no reason other than rationality to adopt moral behavior in my opinion and if it is irrational to be moral then I would think a lot of people wouldn't be. Going against the moral norms is essentially taking a bet, and there is risk and reward with any bet.
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This is not necessarily the case. My argument is there is no fixed set of "moral thing to do" that everyone is born just knowing. People discover the "moral thing to do" by trial and error or by observation. The reason people do the "moral thing" is so they can be perceived as a "moral person" by the "moral community". There is no inherently moral thing to do, but there is a normal reaction. Most people will want to take the normal reaction regardless of whether or not they agree with how it feels. Conformity is what is behind morality.
If someone found a wallet and there is no possibility of it ever being detected in the future by anyone that they took the money then a lot of people will take the money. Why? Because the risk vs reward ratio would skew far in favor of taking the money. But if a person seeks respect from the moral community (people who apparently think like you do) and the odds of it being detected that they took the money in the future are high that it could get back to you someday, then they will not take the money so as not to ruin how you perceive of them and so as to not harm their reputation.
The individual we speak of does not need to have a feeling one way or the other about the owner of the wallet and merely has to think about their own consequences to take either action A or action B. The risk vs reward ratio in my opinion determines what action a rational consequence based person might take but even that might not always be the case as a rational consequence based person isn't rational 100% of the time. Say for instance if they know the person who owns the wallet and it's their friend, well now they might not be as rational.