Abusing Witnesses in Front of the Grand Jury

Is it okay for a prosecutor to abuse a defense witness in front of grand jurors? It is as long as the court gives a limiting instruction. See Bank of Nova Scotia v. United States, 487 U.S. 250, 259-61 (1988):

“We must address, however, whether...there was any misconduct by the prosecution that otherwise may have influenced substantially the grand jury's decision to indict, or whether there is grave doubt as to whether the decision to indict was so influenced.

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The District Court found that a prosecutor was abusive to an expert defense witness during a recess and in the hearing of some grand jurors. Although the Government concedes that the treatment of the expert tax witness was improper, the witness himself testified that his testimony was unaffected by this misconduct. The prosecutors instructed the grand jury to disregard anything they may have heard in conversations between a prosecutor and a witness, and explained to the grand jury that such conversations should have no influence on its deliberations. In light of these ameliorative measures, there is nothing to indicate that the prosecutor's conduct toward this witness substantially affected the grand jury's evaluation of the testimony or its decision to indict.”