Taken as a whole, I think the Tales reveal how very different people can be, even when they appear similar on the outside. You certainly see examples of both moral and immoral individuals, and often the moral ones are not who you might expect. The Pardoner should be focused on sin and saving souls, but he almost seems to encourage sin in order to raise more money. The Parson, on the other hand, is very moral. So, the job doesn't seem to determine the morality.
However, I agree with the others that each tale has its own moral and clumping them together is not the best way to study them.