That is not the Nihilism I am referring to.
Nihilism that I am referring to is "Devaluation of Values", Nihilism is the process of Devaluation. Nietzsche defines it has "The Highest Values being Devalued", this is a process, and he defined it as Nihilism and the Value being devalued was God (God as Value) within European Culture.
That Definition of Nihilism is really Existential Nihilism. There are many forms of Nihilism, Political Nihilism, Legal Nihilism, Moral Nihilism, among many others.
I know what you are trying to do, definition: BOOM! I am Wrong!
I have studied Nihilism for the past 10 years, Nietzsche, Heidegger, Vatimo, and many other philosophers who have written on the subject. Nihilism is not used as you defined, and by the way, that is a fallacy, it is called an appeal to authority.
Protestantism is Nihilistic, because, it was born out of Nihilism. In simple terms, when The Ottoman Empire captured Constantinople, all of the Greek Philosophers and Scholars came to Italy and it triggered the Renaissance. The Renaissance occurred because two hundred years earlier Thomas Aquinas settled the Aristotle Issue within Europe. Which Martin Luther would destroy!
The Greek Philosophers and the Established Aristotelian Theology of the Catholic Church merged together, it sparked the Renaissance. The same thing happened in the 800's with Islam and it happened again with the American Revolution. Theology and Philosophy merged together in the proper context and the Islamic Golden Age was born and the Renaissance was born, and the American Revolution took place. That creates a very high valued Temporal Value that will decline. That decline is Nihilism.
The Reformation was born out of that decline, because, it was an antiphilosophical movement, just as its counterpart was antitheological The Enlightenment. Martin Luther almost singlehandedly upended Europe. Europe spent almost a thousand years settling the Plato/Aristotle struggle and Martin Luther upends it in a few years, almost completely destroying the legacy of Aristotle.
You want sources? I will give you whatever source you want for everything I just said. I hope you like to read!