Whenever people write in barely disguised gloating about “the end of white Christian America,” they are spiking the racial football, not the religious one. The only reason why they include “Christian” as a synonym for “not Jewish.” You should have responded racially, and you did at first, but then you made the mistake of mostly responding religiously.
In the spirit of “oh well,” I’ll add my two cents to this part:
Robert Jones apparently thinks that in order to increase membership churches need to abandon opposition to same-sex marriage and build “diverse” multiracial congregations.
Build diverse multiracial congregations? When are those ever successful or sustainable? As far as that goes, only one race is trying, and you can probably guess which one. The truth of the matter is that the only kind of churches that have “diverse multiracial congregations” are either cults that often end badly (Branch Davidians, Jim Jones’s People’s Temple) or are ridiculed (Jehovah’s Witnesses), or theology lite megachurches that are nothing more than businesses and conglomerates that operate under the veneer of religion and spirituality. Most people are in no mood to join or patronize either.
Otherwise, Sunday morning being the most segregated time of the week is still just as true today as it was in the time when Martin Luther King noted it.