I would like to make a distinction here between pragmatism and metaphysical truth(s).
From a pragmatic standpoint and living in a society in which various people from various cultural and religious backgrounds live I believe that many of the -ism you mentioned, along with several others, will help society a lot to allow us to live in peace with one another and are perfectly usefull as guidelines.
However, from a philosophical standpoint I can only say that they are substitutes for what we deep down are all looking for: perfect justice. These need not to contradict one another in most cases (especially in every-day situations), but historically seen they are the replacement of divine opinion and the large variety of theories of justice show that to find a replacement isn't easy to say the least.


Now another fair question, but here reality blurs the philosophical question.
The fact that many people claim to know the law of G/god(s) and that these laws vary in a sence does not mean that there is no God or that God cannot write and/or communicate a law.
The only solution appears to be special pleeding for one religion and that is what I would prefer to be doing, but not only on the basis of the law that goes with it, but also on internal consistency, experiential reality and other criteria which make it plausable.
This special pleeding would imply that one religion is very close to presenting this law and the others have eighter some distortion of this law, or have a human-made law which is being appealed to as if to a divine law.
The answer than is no, except when one is a polytheist and than you have just asked the Eutyphro question which noone can answer.