There are dynamics involved. It's one thing to deflect meaningless and obviously false accusations, and then there's that constellation of accusations where, even then, they jump to the defensive every time, especially when they find themselves confronted with uncomfortable, or accusatory questions and statements that should be given more thought. Rather than to answer, the individual leaps to the defensive option.
I won't go into a bunch of scenarios, but I will cite one example that actually happened: A minister of a large congregation in a certain city in America was found to be involved in a wife-swapping ring. When he was confronted by one individual in the privacy of his own office, he threw the guy out, threatening to call the police. Later, when confronted by that same man and a deacon and elder, he threw them out, demanding that it was all false. His anger and overall mannerism told them all they needed to know.
You see, how he handled the accusation is what was to very telling. Some would say that if he were truly innocent, then he had every reason to be angry. Rather than to be calm and confront the accusation with level-headed questions for specifics, his guilt was evident in his demeanor and anger. Guilt always has ways of betraying itself. I'm sure Bob would have some insights into this through his years of experience with people and accusations he has seen leveled against others, or perhaps even himself.
Others might say that, given the magnitude of the accusation, the angry response is justified. For myself, if confronted by someone with that accusation, I would be mystified, knowing good and well it's false, but to leap to the defensive, with anger as the fuel for the fire, that would be self-defeating. Sometimes the accuser has an agenda, especially if the accusation is false. Drilling down to the root can be very difficult, but defensiveness isn't always the response that's reasonable nor indicative of innocence. Defensiveness is a wall designed to try and bloc other's view into the truth of a matter, or to cover other avenues of guilt that may exist.
MM