Really? I beg to differ. Many slaves, even in the real world, came out of bondage or have ancestors who survive bondage and have an immense sense of pride in that fact. They are a proud race if you read about them.
Eh? Pride in perseverance is not even in the same ballpark as affection for ones' own captors. Assimilation, then, is a whole different sport. We don't here much out of the Sabines much, remember.
Anyhows, Bretons are diverse and rather fractious, with Merrish ancestry, influence, and overall cultural currency being largely localized in the south, with Iliac bay and Direnni Tower. Whatever the case, we're not operating on the one-drop/one-percent rule. Bretons are Men, just like Cyrodils are Men, and not Tsaesci.
And the Light v. Dark Dichotomy just doesn't gel with Elder Scrolls. Not even amongst the Nords, for whom all Mer are 'dark'.