The trouble is that there are multiple meanings of "moral values" here. There is the human instantiation, and the ideal decision agent instantiation. The ideal decision agent instantiation is used in 5. and a bit in 4. The human instantiation is used elsewhere.
Though usually these are pretty close and the approximation is useful, it can also run into trouble when you're talking specifically about things humans do that ideal decision agents don't do, and this is one of those things.
Specifically, 5. doesn't necessarily work for human values, since we're so inconsistent. People can go into isolation and just think and come out with different human values. How weird is that?!
I think you are right to call attention to the issue of drift.
Drift is bad in a simple value - at least in agents that consider temporal consistency to be a component of rationality. But drift can be acceptable in those 'values' which are valued precisely because they are conventions.
It is not necessarily bad for a teen-age subculture if their aesthetic values (on makeup, piercing, and hair) drift. As long as they don't drift too fast so that nobody knows what to aim for.
I just had a long conversation with my brother, a devout Christian. With my help he has outlined the following argument why it might be good for me to follow Christian deontology:
What do you think?