Well, that's a big weakness of these theories, I think. My question is not terribly complex or dependent on unusual or unrealistic situations.

I would also note that sometimes, people operating off a 'psychologist' basis like you've identified, misunderstand the critiques of others as being also 'psychologist'. For example, the Hayekian critique of central economic planning is often characterized as a psychological argument that "people are naturally selfish and greedy". Thus, if you can get them to stop being so selfish, the objection is overcome. However, what the critique is actually about is inherent limits to knowledge and information, which would apply regardless of psychology.