@SethJ, if, indeed, this is the source for the general rule of עשה דוחה לא תעשה, then a source saying that could be the foundation of a good answer. I'm hoping, though, for something along the lines of "God gave us korbanot with motivation X and Shabbat with motivation Y. By having us set aside Y in the presence of X, He's teaching us that Z."
Here's a write-up of this form (in the opposite direction). —
Isaac Moses 27 mins ago