...or "The misuse of functionalism in explaining Model A".
Functionalism postulates that in creating a model of behavior, one does not need to know the absolute reduced attributes of the inner workings of the mind, but rather all he needs to know is the result, and from there he can create an abstract model to fit. This is good, as it helps us understand things that we cannot fully grasp. However, the models people use are often not logically valid, which in turn invites critics to discard functionalism completely. But it is not functionalism's fault; it is only the way people use it that is wrong.
In Socionics, there is a certain trend to see specific behaviors as attributes of specific functions. THIS IS WRONG, as well as hypocritical. The problem with defining the functions this way is that they become purely definitional, thus losing any and all predictive power.
And it is completely unfalsifiable. If a feeling type solves a calculus equation, he/she is said to be using Te (or whatever). Likewise, any other behavior is assigned a functional value. Since Socionics has little predictive power, the value of defining functions becomes absolutely nothing.
Also, the "theory" of Socionics is a complete joke. There is no theory. The only thing we have are observational trends of various people and their behaviors in specific situations. The only thing that we could possibly call a theory is that there are indeed "types". But other than that, Socionics is nothing more than a really bad trait theory.
I could have done better with my critique, but for now I should say that my argument stands.