I believe that the blessings that would have accompanied a lack of racism in the Church and full participation in the Priesthood of all worthy, male members were withheld from black and white members prior to 1978, but I do not believe it was God who withheld those blessings from us. I believe we withheld them. By that, I mean our (White) inability to accept the will of God in this matter kept blessings from being available to all of us (Black and White). We (White) kept those blessings from being given; in a very real way, we (not God) withheld those blessings from our black brothers and sisters. While the blessings our black brothers and sisters lost (and they literally were lost, as they had been given during Joseph Smith's lifetime) were more obvious and directly painful than those the white members lost, those lost by the white members were no less central to a full implementation of Zion and internalization of godliness, in my opinion.
Full racial equality is part of our modern-day vision of Zion (or at least it should be our individual vision and is the vision of the prophetic leadership), but I think the analogy of Israel being denied entrance into their Promised Land is a fairly good analogy for us being denied entrance into our own modern “Promised Land” until our own generations are prepared to enter it. I believe that general principle still stands and has other applications that we must address - by realizing the incorrect traditions of our fathers that still persist (the bitter fruit that still must be pruned from the vineyard) and doing everything possible within our own spheres of influence to eradicate them.