Appropriation is Marginalization:
An (US)American Christian Perspective
Cultural and religious appropriation is an issue Christianity (particularly the USAmerican kind I am a part of) needs to seriously, carefully, and humbly consider. And part of that consideration is to listen and hold the witness of those marginalized (through appropriation and otherwise). The main way to know appropriation is happening is by hearing the manifold stories coming from those signaling appropriation. Of course, I am saying this with the bias of being one from a country the victim of (USAmerican) imperialism, cultural propaganda (Americanisation), and appropriation.
It does not matter what strand or denomination of the appropriated culture is calling it out, nor does it matter how liberal or progressive the appropriating tradition could be. Those who are called out as appropriating - especially as an invitation to conversation, and to right a wrong - ought to only listen and seek to right the wrong. Accepting that invitation to conversation could be the more effective way to strategize righting the wrong. Often, USAmerican liberals and progressives default to defending our intents. Intents do not matter. The harm that may be caused is what matters.
I do not expect this depth of reflection from liberals. I do expect this depth of reflection of US political, social and religious progressives. If our aim as progressives is equity, inclusion, and justice, then we need to listen to how many are being marginalized - politically, socially, economically, and culturally. Appropriation is a form of marginalization. It is the marginalized who get to define appropriation.