The term “theory” today is often used to mean Postmodernism theory or just Postmodernism. And because of this Postmodernism is often accused of high jacking the term. But that is just plain wrong.
In acts of elitism this may have occurred a century ago and can be said to still be practiced today. The term “philosophy” could be seen as one such word. Today it represents only the Western tradition (Russell, Kant, etc) and quietly excludes Eastern thought (Confucius, Vasubandhu, etc) all together. But theory is somehow different.
Theory as a term to be used as a stand-alone term represents a set of values, those of Postmodern thought, and it was not used in this manner until Postmodernism came along. Through an act of defamiliarity it has gained momentum through usage. And there is nothing wrong with this. As Postmodernism labours to point out words only have meaning insofar as a series of differences.
A word can be said to be relative to all usage within a language or even against all languages. I do not see there is snobbery or elitist tendency in Postmodernism’s appropriation of the term, but rather it has been seen as misappropriation and that it is a misunderstanding of Postmodern thought and its non-hidden agenda. It is a case of theory of relativity as well as being the relativity of (the term) “theory”.