It has always struck me as incredibly arrogant when audiences insist on singing their own versions of choruses.
I have in the past, stopped singing and insisted on them either singing my chorus (and teaching it if necessary) or not singing the song at all.
Walter Pardon had to drop two songs from his repertoire (one of them his favourite), because audiences did this; and it also upset him when they ignored the speed he sang and dragged out the choruses.
Don't know what he'd have made of the eejits popping their fingers in their cheeks!
Jim Carroll