I'm going to have to in a completely unexpected and uncharacteristic move say that I think the answer lies somewhere in the middle
.
I think it's fine to acknowledge that Churchill (along with the rest of the ruling class across most of Europe at the time) had white supremacist tendancies. It's not irrelevant to understanding the history, in fact, it's quite relevant and important because it helps us to understand HOW something like Nazi Germany happened, when otherwise it seems unfathomable. Essentially that Hitler's ideology was a twisted, wildly exaggerated and violent offshoot of a mindset that was
sadly not that uncommon at the time. Basically, a lot of people BELIEVED in racial supremacy and the "ubermensch" ideology (of selective breeding being ideal) was widely held as being scientific truth.
It's important to remember because if we re-write the history to be that Hitler was a lone crazy person with wildly unusual ideas who somehow got into power, we fail to understand that it could happen again.
It doesn't alter the facts when it comes to the military victory which really has very little to do with the ideologies of the people involved. It just opens up the very uncomfortable notion that someone could be BOTH a racial supremacist AND fighting for "good", when in a historical context, that's extremely likely... since most people believed it, and it stands to reason that they weren't somehow all evil.
I would guess it's simply "too recent" for the history of WW2 to be viewed in purely accurate / academic terms, though... in a few hundred years time, I would imagine that people will be far more comfortable discussing it in the same way we discuss Medieval wars and kings now, i.e. out of pure historical curiosity without the attached sentiment and "national pride" that comes with more recent history.