“I think there’s no serious doubt that an objective “now” actually exists”
Ein and Stein prove this incorrect. Here is a cool little modeling tool that lets you play with time dilation based on speed and distance traveled. You will see that Ein and Stein age very differently. How can they be said to have an objective “now” shared between them?
http://www.pbs.org/wgbh/nova/einstein/hotsciencetwin/
How can it be said they don't? The "'evidence" in play does not seem to be dispositive either way....