::::::::Take Tgr's previous example and choose another point instead of C (call it Y, for example) and redo the analysis. You get exactly the same result if Hubble's Law applies universally. Y then acts exactly the same way as C and is therefore indistinguishable from C. For that reason, Y must either "also" be the center or there must be no center at all. There's really nothing more to it than that. A center implies a breaking of symmetry that is impossible in a Hubble's Law arrangement.