Bullshido Argument #20 - The Unresponsive Subject.
This argument/strategy relies on the subject avoiding direct invitiations to participate in the investigation. Such a strategy can be used under several pretenses.
1) The subject can claim not to have been aware of the investigation.
Counter - The best counter to this is an invitation or series of invitations issued via email or message that can be traced with a return receipt to show that messages were properly delivered to the subject's email address.
2) The subject can acknowledge the investigation (either through email or on another website) but refuse to take part.
Counter - I would suggest repeated (but not incessant, harassing) invitations, such as politely posting the questions that have been raised on a forum where the subject frequents.
Whether or not the subject ultimately refuses to take part, it is important to show that they were, in fact, aware of and invited to the investigation.