He was charged with conspiracy, so it's relevant that it was discussed. Conspiracy usually requires discussion of the intended crime, and then at least one party to commit an act that furthers that crime. It doesn't actually require the crime itself to be committed.
From what I read in another article there were various nasty and/or more clearly criminal things that he discussed/joked about doing although from what I understand he didn't actually follow through on them and they just released the information to journalists to make AT&T look bad.