To accurately answer this question, one should know and understand what has gone before in terms of the court's decisions and its attitude toward witnesses. Judge Danforth has assumed a dictatorial position and his word is law in all senses of the word. His authority cannot be challenged and he has already rhetorically stated that he believes that the voice of God is speaking through the children. This means that he believes that they are, by default, innocent. In his eyes their veracity cannot be questioned and any attempt to do so is regarded with skepticism and suspicion.
It is because of the girls' testimony that Martha Corey, Elizabeth Proctor and Rebecca Nurse have been arrested and charged with consorting with the devil. When John Proctor presents the testament containing the statements of ninety-one citizens vouching for the good character of the three detainees, Danforth is immediately on his guard. He is already suspicious that John Proctor's sole purpose is to disrupt proceedings and is quite skeptical of him since he has failed in trying to bargain with him about Elizabeth being pregnant (he said she could be released for a year if John withdrew his charge about the girls' lying).
When John presents the testament to him, Danforth, at Reverend Parris's desperate urging, orders Mr. Cheever to draw up warrants of arrest for all ninety-one whose names appear in the document. He states that they will be arrested for examination.
This obviously means that the people so named will be apprehended, brought to court and interrogated aggressively. One can assume that Judge Danforth will under no circumstances allow his judgment and authority to be brought into question. He is much too arrogant to even have others consider that he might be wrong. As far as he is concerned, he is an angel of good and, therefore, cannot be tarnished by the stain of indiscretion; God is on his side and he is doing His work.
It is easy to conclude that all of the ninety-one citizens named in the testament will be intimidated by Judge Danforth's authority and his dictatorial posture. They will be at a great disadvantage and will be relentlessly pursued in cross examination. Since these are honest, noble, and hardworking citizens who believe in doing good, their integrity and morality will, more than likely, be brought into question and many of them will, most probably, fold under Danforth's bullying and Reverend Parris's consistent meddling and whining. In the end, many of them may be charged with witchcraft, ironically, just as those who they wish to defend had been.
It is this outcome that is Mr. Nurse's greatest fear. He declares that he has brought trouble to these citizens, but his claim is dismissed by Danforth, who tells him:
No, old man, you have not hurt these people if they are of good conscience. But you must understand, sir, that a person is either with this court or he must be counted against it; there be no road between.
These words bring no comfort, though, and must surely strike fear into the hearts of all those who hear them and are there to defend those whom they love. It is at this realization, perhaps, that Mary Warren suddenly sobs. Her reaction foreshadows her later condemnation of John Proctor.