I haven't read the whole thread, mobile chicanes are common over here too. Bikes, cars, campervans, well anything being piloted by somebody who has never bothered thinking about how they effect other road users or worse don't give a damn.
It's just a lack of consideration, courtesy & awareness. Sometimes just a lack of intelligence & an overgrown sense of self importance.
Avoid them, just like replying to an idiot, they will bring you down to their level. Blame the parents.