With respect to the "good" man who suddenly murders his family, first all actions have weight, it is good to smile at someone, but that good is not equivolent to buying a homeless man a new suit and getting him a job, that second "good" is bigger, and more meaningful.
The weight of good needs to be measured, just in the same way we measure the consistency of actions, to in the end decide, whether one is "good" or "bad".
But I do not really believe any of us are "good", in an deep way, only that we can act good, and be "practically" good, meaning for utility sake you say "John is a good guy" or "Dwayne is a bad guy" and we know what you mean. You dont mean always, and in every instance, only that across time, and all actions considered, they are either mostly "good" or mostly "bad".
Really, I believe we are "bad", in that we "sin", meaning, "miss the mark", and fall short of what we ought to be. This is my Christian faith talking, but again, the question of whether I am practically good or bad is still worth discussing, and then secondly, if we want to move into a theological debate, we can move from "practical" good vs bad, into "obejective good vs bad".
I'd say objectively we all know what is "good and bad", but whether we act what we know or deny it, and do what we prefer, is another question all together.
ie., we know its bad to steal, lie, or kill, but we sometimes knowingly do them anyways. That to me doesnt mean good and bad, are false, or fake, only that we who are free to act, make poor choices, when we act.
who provides the measure?
I don't think that this is necessarily true although there is likely an average. Still, take away any form of self- seeing thinker and I don't know if the universe itself would discern good from bad, there would only be 'possible'.
Why is the Buddha weighted more heavily than the fly?
In your view.
you have now put a price on livesin a ranking system, lives that you can't possible under stand except through your opinion of their importance. So now, which life is more or less important Buddha, Jesus or a child's?