I understand why you're reluctant to identify Wade Michael Page as a white supremacist, but I'm an expert in visual rhetoric and I'm here to help you out. Consider the photograph of Page you're currently using:
There are some subtle clues as to Page's ideology hidden in this image. First:
That is a Nazi flag. You can tell because it contains a Swastika in a white circle surrounded by a red hem. It is highly unlikely that someone hung it because it means "good luck" in Sanskrit. Also:
The repeating patten on that guitar strap is the Confederate Battle Flag. It reminds white people of those glorious antebellum days when blacks were in their place and no real American had even heard of Muslims. Also:
That is the number fourteen. It stands for the Fourteen Words most dear to oppressed white men in America today. Those words are "We must secure the existence of our people and a future for White Children."
So let me assure you: if you have correctly identified the man in the photograph above, you don't need to "speculate" as to whether he was a white supremacist. Because there's no room for speculation. That man in that picture is a white supremacist. Whether his white supremacist beliefs influenced his decision to murder peaceful Sikhs, that may well be a matter for debate. But that man? The one in the picture? He's a white supremacist.