Unless I knew the emails existed I would say "I have no idea what you're talking about, and I'm not interested in talking about it." But more succinctly, with just two words maybe. Something along the lines of "no comment". It's not possible for someone to have made even a cursory glance the history or ubiquity of the phrase "no comment" and honestly claim that it's either not a reasonable approach or not typically done. This just silly.