What is ironic about danforth's statement about witchcraft and court proceedings?

Is this the statement you're referring to?

Is that document in your hand a lie? I will not accept it! I will not deal in lies Mister! You will give me your honest confession in my hand, or I cannot keep your from the rope.... Which way do you go Mister?

If so, the irony can be found in the fact that Danforth emphatically states he does not deal in lies, when in fact, the proceedings in their entirety were based upon lies.