From the scientific view, the theory of karma may be a metaphysical assumption -- but it is no more so than the assumption that all of life is material and originated out of pure chance
We are the makers of our own lives. There is no such thing as fate. Our lives are the result of our previous actions, our karma, and it naturally flows that, having been ourselves the makers of our karma, we must also be able to unmake it.
All major religious traditions carry basically the same message, that is love, compassion and forgiveness the important thing is they should be part of our daily lives.
Who cares for your bhakti and mukti? Who cares what your scriptures say? I will go into a thousand hells cheerfully if I can rouse my countrymen, immersed in tamas, to stand on their own feet and be men inspired with the spirit of karma-yoga. I am a follower only of he or she who serves and helps others without caring for his own bhakti and mukti!