I believe that the level of conviction that we have in a belief is *very* relevant to how we behave.
Although most Buddhists claim to believe in karma, it has been my experience that this belief is not that strong because they also claim to believe in "injustice". These beliefs are contradictory. If karma is real, then injustice does not exist.
When the level of conviction in karma really counts is when we are a victim of something truly horrible and are consumed by the primal desire to strike back.
That is exactly when it matters the most.
Because if we believe with absolute certainty that the people who hurt us will pay and that if we decide to strike back that we would pay our ability to self-regulate our destructive emotions is increased to the level where conflict can be avoided.
Such is the nature of satyagraha.
Think of the consequences of that if everyone held that conviction.
IMHO that is a world worth fighting for.