If there were any belief system that consistently produced saints–that is, if there were any system of ideas of which all its holders behaved, once they adopted said ideas, in observably good ways, to their benefit and the benefit of those they met–there were would be no more argument. All humanity would be naturally drawn to those ideas. All other ideas would die out.
That would be a disproof of nihilism.
But there is no such belief system.