tinker, I do not think it is about "sins". I think it is simply about weighing what the person has accomplished.

For example, a politician. Has he done well or even extra ordiray things for his citizens? As it is his job to take care of them.
To judge him because he has, for example, cheated on his wife, should in this case not come into the eqation, as it has nothing to do with his job.

Now, if said politician is said to be a good person morally, then of course we must consider his infidelity.