Also, this system sounds like it impedes moral progress because it disincentives society to change its values over time

I guessed such a strategy would hasten moral progress. I think of moral progress as the morality of a more sensitive minority impressing itself, over time, on the general population. Do you think of examples that don't fit this pattern? But -- for example -- most people I know aren't vegetarian but I think meat eaters could agree that vegetarians have the moral high ground if it were to be a moral issue. Meat eaters folding to become vegetarians would accelerate moral progress if this is what a future moral society would choose.