So because one party has a problem with intolerance, promoting these things breaks the non-partisan label? Seems a bit like being non-partisan is an end in itself.
It's the same principle as being a non-religious organization. If the ACLU went around telling people that accepting Jesus as your lord and savior is the most important liberty, I suspect you'd agree that's very strange - even though many devout Christians do hold that position and think it's important.
My belief system makes white supremacy not some other, legitimate belief I oppose, but one that is beyond the pale because it threatens the core of my belief system (universal human rights and equality).
Since the (current) Republican Party is running on white supremacy ...