Does that reduce to "economically bad is morally bad"?

Is it economically and morally correct to spend $(x>1)*n dollars to remove a negative externality of $n? (For example, an airport which covers runway repairs by adding a surcharge to fuel sales will result in pilots who buy a lot of fuel for long flights subsidizing pilots who make lots of short flights. But charging a landing fee will require hiring someone to collect the landing fee; the fuel is self-serve.)

If the monopoly had sufficiently high fixed costs and decreasing marginal costs such that it made the most money at a price that is lower than the equilibrium price of a duopoly, would it still be economically bad? Would it still be morally bad?