After being embroiled in the 'When Not To Sing' thread, I've been reading this one with some interest.
Personally, being taught choruses never bothered me too much as long as it didn't go on for too long.
Peggy Seeger did tend to drag it out on occasion; on the other hand, she did have perfect pitch and their repertoire included some superb tunes with quite complicated choruses. When it worked it did so superbly - hers and Ewan's 'Baron of Lys' chorus was always great fun to sing - and after a few sessions of her chorus teaching, the learning of difficult tunes has always been a doddle (for me) and has stuck with me far longer than the learning of new sets of words has, for which I've always been grateful.
One (only one) of the side effects of the abhorrent practice of joining in on every song is that quite often an audience will iron out the subtlties of a tune, especially if it's slightly different to the generally known one, leading to ragged, undefined tunes. I used to sing 'Scarborough Fair' to the Kidson tune which I much prefer to the Mark Anderson one - I know bloody well I would not get way with doing so in a 'singalong' club.
We usually finished the Singers Club evenings with a well-known chorus song, quite often 'The Leaving of Liverpool' or 'I'm A Rover, Seldom Sober'. Both of these have great choruses, but, when draggeed out, can be mournful dirges.
Personally, I would rather spend the minute or so it takes to get the chorus right than let the evening finish with a funereal feel that dragged out, tiredly sung choruses can generate.
Jim Carroll