As I understand BU, unless economical majority finds certain block size acceptable, it cannot succeed. If there are just 75% miners creating very big blocks, it doesnt really matter if economical majority (miners+exchanges+services+people) doesnt accept these big blocks. I know this looks like potentionally fuzy enviroment with a lot of uncertainity, but it could be said giving miners ability to choose what transactions add to blocks might mean they destroy Bitcoin by just creating empty blocks - and the orphan rate risk with today low fees would suggest such rogue behaviour! So dont expect there is interest for the worst to happen all the time.
My question is still unanswered. How can the 'economic majority' (whatever this is supposed to be) prevent a huge block size that most of the miners and nodes are voting in favor of?
Because those who dont allow such huge blocks in their client simply contine on the chain with their choosen maximum blocksize. Although there may be many compelling chains with diferent maximum blocksizes, it doesnt make much sence to using the one what has little support.
At least this is how I understand it, and it is step from today central planning to more freedoom for everyone with the associated responsibility - if you choose wrong blocksize value, you might not be using the chain most Bitcoiners are on.