Er, what evidence exactly am I supposed to be updating on?

The supplied evidence for 1 ("We value extra copies in other quantum branches") seems feeble. Most people are totally ignorant of the MWI. Most people lived before it was invented. Quantum theory is mostly an irrelevance - as far as people's values goes. If - astonishingly - evidence of wavefunction collapse was ever found, people would carry on caring about things much as before - without any breakdown of morality - despite the loss of practially everything in other worlds. That thought experiment seems to demonstrate that most people care very little about copies of themselves in other worlds - since they would behave much the same if scientists discovered that those worlds did not exist.

Maybe there are somewhere a bunch of people with very odd values, who actually believe that they really do value copies of themselves in other worlds. I can think of at least one fellow who thinks like that - David Pearce. However, if so, this hypothetical silent mass of people have not stood up to be counted here.