Claptrap's "minion" thing didn't bug me because Claptrap is a deluded idiot. Him thinking we're his minion was funny because it was so clearly wrong.
Brick calling us "Slab" bugged me more. Claptrap being dumb and thinking we work for him was funny. Brick not being as dumb and thinking we work for him (and being right, but working for him isn't the same as joining his stupid bandit tribe) was less so.