Whilst your complainant seems to have a bee in their bonnet I'm not sure you're doing anyone anyone any favours by CC'ing pseudo-private correspondence into a mailing list.
As a fellow ISP owner running Tor Exits (AS28715) I also enjoy the "right" to treat abuse requests according to rules that only I write (UK legislation not withstanding) but IMHO we have a responsibility proportional to our "mere conduit" superpowers, both to the privacy of Tor users *and* crazy abuse@ emails from individuals.