There is a form of avak loshon hora that can result from one’s keeping the laws of forbidden speech. If one says that he is reluctant to discuss a particular individual so as to avoid speaking loshon hora, he is, in effect, communicating that he knows something negative about that person.
“I’d rather not discuss So-and-so,” is avak loshon hora.
When faced with such a situation, a person must either attempt to divert the conversation to another topic or indicate that he does not know any pertinent information about the person under discussion.