The blackhole list admins are completely correct (Score 0)

His e-mail server isn't secure (it's accepting forged e-mails), meaning that it is a potential spam-source. Configure your server properly, end of problem - Anyone who runs a server exposed to the net needs to be sufficiently experienced to properly configure it - else they deserve what they get. The worst part of all of this, is that the guy won't even acknowledge that there is a problem, his reaction is to look into legal recourses. The morale of the story: if you're ignorant, sue to change the system.