drift is harmful from the perspective of my current values
True. And that drift would be beneficial from the perspective of your new, drifted-to values.
But neither of those statements have any bearing on whether value drift (in general or any specific instance thereof) is good or bad.
It's good measured by the new values and bad measured by the old ones. What other standards of goodness do we have at our disposal in this problem?
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?