“BANTERING CHAPS”. The poet in the Clive James poem expresses a preference for the “ease of bantering chaps” and adopts a cheeky tone. (It is an “ex-sparrow”.) Thus James reflects the cheeky tone of Catullus. This wikipedia entry classifies the type of 50 out of 116 poems by Catullus as “invective” and the type of another 20 as “friends”.
Catullus 16 had the honor, as this post by Ted Scheinman reports, of having its first and last line—the line is repeated—bleeped out on NPR (in both Latin and in English translation!). Mary Beard explains the Catullus joke here.
You can see how Catullus would appeal to an adolescent.