Why should non-trinitarianism preclude one from being considered Christian?
Using the Nicene Creed as the standard would lead to that conclusion.
So for example Origen or Eusebius of Caesarea weren't Christian? Weird standard.
Yeah, it does seem a little arbitrary. As you know, people like Origen who predate conciliar definitions usually get a pass, except when they don't. I was under the impression that Eusebius accepted the Creed. Do you have a source that says otherwise?
You might be right. I only know that he was suspected an Arian, hence his lack of canonisation.