It's not "shooting the messenger." That phrase is properly used only when the messenger is delivering the truth and the truth enrages the person who is now informed of something he does not like. Calling Youssef a "fool" and/or a "charlatan" because the message isn't true at all does not fit the proper context.
And thus, the comment "So, your solution is to shoot the messeger?" doesn't make any sense as a response to what was aready said.