This is a court case, not Pardon the Interruption. Kessler's job is to get Brady the best possible settlement or decision that is in his capability as a legal representative, not to salvage the reputation of the Patriots by convincing some judge that they aren't cheaters. Whatever line of answers is most likely to benefit Brady is the correct line of answers. Kessler is a high profile lawyer who probably came to the conclusion that directly contradicting the premise of the question and arguing with the judge over whether or not McNally deflated balls would not serve the best interests of his client in this case.