Dione - I think we need to agree on some definitions, because you are saying stuff that makes no sense to me.
Rational = Based on or in accordance with reason or logic: "a rational explanation"
Irrational = Without the faculty of reason; deprived of reason. Without or deprived of normal mental clarity or sound judgment. Utterly illogical (irrational arguments)
Therefore, you cannot call someone's reasoned decision based on personal preferences "irrational", no matter how much you disagree with that decision.
In contrast, it is irrational to believe that the Earth is a few thousand years old, while knowing that there are million-year-old fossils in the ground. Because the two are contradictory and accepting them both requires complete disregard for logic and reason. Hence, irrational.
I have used the terms trade-off and utility function because I have studied Economics as well as Game Theory. Both fields of study work with rational players acting in a rational way, who part with a cost (price of a restaurant meal) in expectation of the desired payoff (enjoying a pleasant evening at the restaurant).
I realize that these are alien subjects to you so understanding is not likely to come quickly or easily, but please look them up and try to familiarise yourself with these concepts. They will be invaluable tools for you to make sense of the world you live in (and understand that it is not an irrational place).
"you have employed the defense mechanisms of rationalization (you accept the trade off)"
You think so because you don't understand what the term trade-off means and how it is used in context. It is a perfectly normal term to use when talking about rational choices, as anyone who has ever studied the subject can tell you.
"From what I have seen creationists use exactly the same processes to justify their belief that the world is only a few thousand years old."
I would be surprised. Tell me, what kind of process do they used to justify this belief? Trade-off of what? "Intellectualisation" how?
"The most rational people in our society are psychopaths."
And you know that because you are intimate with so many psychopaths? 
You have clearly never studied nor in any way understood decision-making processes, which is fine, I don't mind sharing the information. However, you need to refrain from making silly sweeping generalisations like the above which completely undermine your credibility, imho.