I think my lifting a couple excerpts from Spencer's book might have made it easier for his ideas to be mischaracterized - sorry about that. Of course, if you take WWJD absolutely literally, there are a whole number of logical objections. Spencer refined this a little more and preferred asking "If I spent 3 years in the company of Jesus, what would I think about ..."
One of the most obvious rebuttals to the simplistic WWJD? approach is to ask, "Would Jesus get married?" Well, no -- no he wouldn't. But does that mean nobody ELSE should get married? Okay, fine, sure, any number of the Church Fathers took a dim view of sex and marriage because it meant you could never be a monk, or whatever. But seriously: who today would take that position? Even the most traditional churches out there have sacraments for marriage and the baptizing of children -- despite the fact that Jesus himself never had a family. Is this supposed to be a bad thing, now?
Spencer's objecting to churches who focus on size and growth, who focus on your church attendance as an indicator for how spiritual you are, and who focus on getting involved in little programs inspired by whatever is the latest bestseller at the Christian bookstore. There is a large, large number of churches who do this. But yes, Christianity and attending church is about far more than that. What's useful to understand is a lot of people (rightly or wrongly) leave the evangelical church because they are sick of what they are expected to do and focus on while they go there.
In other words, when Spencer talks about "the Christian religion", he is referring specifically to topical studies, building programs, capital campaigns and attendance figures? Um, wow. That seems awfully reductive -- and probably, in some ways, culturally narrow.
True. Although I'd suggest Spencer is rather making an argument equivalent to saying that a marriage without sex is wrong. Where the analogy breaks down is where your commitment to one particular local church or denomination is not the equivalent to the commitment you make when you get married. The American Evangelical church as a whole is suffering right now from a whole number of problems. There's a reason a large number of believers are leaving it. I'm not one of them, but I understand why they are doing it.
If "I'm not religious but I'm a very spiritual person" equates to "I'm not married but I'm a very sexual person", then it sounds to me like Spencer is almost making an argument equivalent to the idea that marriage kills romance, so we should always stay romantically involved with someone -- we should keep on dating them -- but without actually marrying them. Because once we marry them, we have to deal with, y'know, all the annoying nitty-gritty stuff like where we hang the towels and who gets to pick up the dry-cleaning and all that other boring stuff.