This argument could have been used to discourage people from discussing the need to make any ethical improvements in our society, including, for example, ending

This argument could have been used to discourage people from discussing the need to make any ethical improvements in our society, including, for example, ending slavery. The power of enforcement follows from policy, in a democracy policy is influenced by public opinion, public opinion is shaped by discussion. We ought to discuss moral issues for which there is currently no enforcement.