Bad arguments that people are irrational

There are psychologists and economists, such as Daniel Kahneman, who have made their reputations on the thesis that humans are irrational. He got famous with a Bank of Sweden prize for it. Here is an example:

2. A team of psychologists performed personality tests on 100 professionals, of which 30 were engineers and 70 were lawyers. Brief descriptions were written for each subject. The following is a sample of one of the resulting descriptions:
Jack is a 45-year-old man. He is married and has four children. He is generally conservative, careful, and ambitious. He shows no interest in political and social issues and spends most of his free time on his many hobbies, which include home carpentry, sailing, and mathematics.

What is the probability that Jack is one of the 30 engineers?
A. 10–40 percent
B. 40–60 percent
C. 60–80 percent
D. 80–100 percent

Lawyers do not have mathematics as a hobby. Engineers often do. That is what I thought. Kahneman says that I am irrational for thinking so. He says that the right answer is A.

I don't doubt that people can be fooled by trick questions. Most non-mathematicians are not even able to answer straightforward logic problems.