Your argument about mangoes has a very big assumption involved and that is the supplier wants everyone to have mangoes and isn't in the market just for the profit. This is similar to what Reagan tried to argue with the Trickle-Down economics, he said if you tax the rich less they'll create more jobs and hence it'll benefit everyone. This didn't happen, 'cuz the rich found other better ways (investment funds etc) to use that extra money than create jobs. So, NEVER assume intrinsic goodness. If discriminatory policies are allowed people will misuse them.