I can agree with much of what you said, but when I began watching the game in the mid-Seventies the slow hand clapping often used to begin in the Grandstand (accompanied by slow stamping of feet on the old wooden floorboards). That's where I was with my old man and my uncles and we were surrounded by some of the club's wealthiest fans.
One guy in Block C of the Grandstand, who used to smoke huge cigars and wear big sheepskin coats during the winter, was often the origin of the 'what a load of rubbish' chants. He was extremely vocal and often very funny too as I recall. As it happens, my mother was laughing about him just last week. Apparently, when me and my father got back home after games, I'd report to her about the antics of 'the big shouty man' as often as I would about the team.
The slow hand clapping was occasionally aimed at the opposition as well as the home side if the game was boring. It's something which seems to have disappeared from the game altogether. Shame, because the game against Fulham and the visitors in particular would have been perfect targets for the old slow hand clap.