[hackerspaces] any recommendations for handling of a troll?

[Peter]

hi,

i am member of the small hackerspace in bremen/germany:
  hackerspace-bremen.de

here in bremen lives a person, an underemployed journalist, quite 
capable of writing, but only focused on old electronics - he is the 
inventor of the quote
"Die heutigen Kids löten nicht mehr" - "The kids of today don't solder 
any more" (we have three soldering stations and more soldering irons..)

He was trolling our public mailing list, always with similar arguments, 
killing some threads and causing disturbances. We kicked him from the 
mailing lists.
He then threatened to use some pseudonyms to get access again.

He is also active on some forums and on the usenet. there he started 
complaining about hackerspaces etc, embedded in his other thoughts.

Now the question is:

should we ignore him, or should we do something proactivly?
He is learning-resistant, talking with him was never frugal and only a 
waste of time.

my idea is always: act by what he does next, if he posts something bad 
anywhere, ridicule him. if he keeps quiet: excellent!

any recommendations? is there an anti-troll-RFC or anything?
have you encountered similar or other trolls, how did you handle them?

greetings, peter