The Jargon File (version 4.4.7, 29 Dec 2003):

dahmum
 /dah'mum/, n.

    [Usenet] The material of which protracted flame wars, especially those
    about operating systems, is composed. Homeomorphic to spam. The term
    dahmum is derived from the name of a militant OS/2 advocate, and
    originated when an extensively cross-posted OS/2-versus-Linux debate was
    fed through Dissociated Press.