Irony or Obvious Command?

Reading through Matt 23.1-3 this morning. Is Christ' s command to practice and observe whatever they [scribes and Pharisees] tell you, an instance of a clear command delineating the difference between what they say [good] and what they do [bad]? I think I side with those who think that Christ is using biting irony here (Expositor's Bible Commentary for one), because Christ does emphasize whatever they tell you, then he proceeds to condemn all that they do. The Pharisees and scribes lived not only according to the Torah (Gen - Deut), but also according to the oral traditions which Christ condemns over and over.

Tom Constable describes the passage this way: Assuming the consistency of Jesus’ teaching we should understand His words here as ironical. This interpretation allows the Greek aorist verb ekathisan (“to sit,” v. 2) to have its natural force. This view also explains the chiasm in verses 2–4 in which the first two statements constitute irony and the second two give non-ironical advice.

A The leaders presumed to take on Moses’ teaching authority. v. 2

B Do what they say. v. 3a (irony)

B’ Do not do what they do v. 3b (non-irony)

A’ Their teaching merely binds people v. 4