Interest have two components:

1. The percent confidence you have that the interest can accurately be ascribed to the majority of those who agree or disagree
2. The percent you would consider that a valid interest. For instance the desire for revenge is less valid than the desire to provide an honest living for your family. You say who are we to say that an interest is valid or not? Well we do it all the time. We say that your desire (interest) for neighbor's flat screen TV is not valid enough that it can over-ride your neighbors right to their property. It is better to get this debate out in the open and debate which interest are valid, instead of pretending that the law is going to let us all do whatever we want.