Depending on the view of things, this might be more consistent, but I cannot see how it could be ethically superior. The other alternative would be that you are allowed to openly criticize a system, but only if you do not exploit it yourself. This tastes of hypocrisy. Remember, we are talking about rational individuals, not saints. The book makes it clear how ideologically contaminated the international debate on social organization still is, and how far we still are from a pragmatic view of things.
Markets are undeniably very powerful tools to create wealth, and they have served the world well.
Societies that have put their bets on central planning have fared dramatically worse and practically ruined themselves. Markets are valuable tools indeed, but they are only tools, not ends in themselves. And as such, they cannot be the universal answer to all problems. As for commerce, this principle is indeed sensible and useful. However, it is hard to believe that extending market values to all aspects of the world will increase total utility.