Virtuous intelligent people, the wise, are habituated and developed in the direction of truth and away from lies, deceit and bullshit. They have a sensitivity to the truth and the value of truth. Bullshitting requires and in turn reinforces a kind of mental dullness and blindness. It leads to a kind of degeneration of the mental faculties. If you don't care about the truth—only the parochial effects of your petty machinations—then you are frustrating the intellect and its grasp of reality. You are reinforcing vices while weakening the capacity for discernment and the strengths and virtues needed for proper intellectual function and receptivity.
It's a bit like what happens when an intelligent coward is met with contrary evidence. He will turn away from the truth and go to great lengths to rationalize it away, and in doing so, he will blind himself to the truth. Making that a habit through repetition only deepens the vice and unravels the mind, making it increasingly difficult to dig yourself out.