One proposition implicit in Festinger’s theory is that we don’t always behave based on what we believe; rather, what we believe may be the result of how we have already behaved.This proposition seems to me a chicken or egg scenario.
In my view the most common behavioural explanation behind many posts on this forum are displacement theory, transference and denial.
In laymans terms - Johnny always got told what to do when he was a little boy by his father. Therefore when we give Johnny good advice, we remind him of his father. We become the father and the repressed impulses are redirected toward the poster. Denial and self delusion become the remedy of choice and the basis for an outstanding audio system - 'the best I've heard'.