Recognizing that I am working with generalities here and that generalities always do a disservice to some people who identify with the group, for me 'Left Behind' has come to describe a particular type of church goer. (I use 'church goer' here because I find that some of the people, while they might identify strongly as Christian, exhibit far too many actions that call to question the authenticity of their identity. They do, however, tend to be very good at going to church). This group believes that one day those who have not been 'good Christians' will be separated from the love of God – left behind as all the 'good' people get sucked up in God's magical, over-sized Hoover (actually probably a Dyson, I can't help but believe God would have upgraded by now). That may not be exactly how they would put it, but you get the idea.
Along with this perspective comes a few other... well, let's call them personality quirks. Frequently, Left Behinders have a quiet (mostly unspoken) air of superiority. Let's face it, if you know you are going to be saved (sucked up by the Holy Dyson) and that others are going to be left behind to wallow in their heathenness... it would be sort of hard not to feel the littlest bit superior. Along with that comes a few things: very little spiritual growth because they already have it right, a general sense of entitlement, resistance to 'other,' resistance to new ideas (or change), and the ability to be thought of as 'nice' without actually having to consistently demonstrate love of neighbor and enemy.
This all creates a problem with moving the church forward. I have to completely agree with John Spong's assessment that the Church must change or die. As a matter of fact, I am no longer interested in participating in arguments that suggest otherwise. There is much work to do and anything that distracts from moving forward puts the Church that much further behind.
That's the crux of the problem. As a church tries to reclaim the foundations of Christianity (to reassert the necessity for love of God and neighbor and those we may perceive as enemy; to actively minister and worship with those who have been marginalized; to stand up to the status quo, hypocrisy, piousness, and those who take advantage of 'the least of these'), we meet great resistance from two places.
The first is the Left Behinders, who do not like the change that comes with doing all of those things. What the change looks like can be offensive to people who believe they already have it right. It confronts who they have been for years and can even suggest to them that they were wrong. Understandably that can introduce doubt in a place where there had only been blessed assurance that they had their one way ticket to the Holy Dyson in the sky. It also means letting in people who may have previously been thought of as outsiders, 'others' and quite possibly the ones that would miss out on the great vacuum ride to the heaven.
Typically, the Left Behinders, have established some place of power, prestige or position and the change needed in the church to avoid slow death threatens those places. They are likely to hunker down without any real regard to the theological soundness of the movement forward (or movement back to biblical foundations) and will cherry pick verses, make appeals to tradition and even demonize the leaders of the change. Their reactions are completely understandable considering what they believe and how they have experience Christianity thus far. It also happens to be a path whose tangent would continue to lead the church further and further away from it's calling...and it is not acceptable.
The second resistance will come from those who agree with the need for change. They tend to have a real passion for the life and teachings of Jesus and in their own lives you can see those teachings mirrored in their passion for those some might think of as 'other.' These are people who have frequently themselves been marginalized within the traditional church; their voices, while allowed to be expressed, are lovingly (possibly 'nicely' is a better word) minimized by the Left Behinders who hold the power.
As change begins to be realized, it is this group that will put up the most earnest and biblical arguments to slow the change down – they don't want to leave the Left Behinders behind.... ironic, isn't it? ... (and we're not even done with the irony yet). Their love of neighbor will lead them to advocate for those who, in one form or another, had previously 'nicely' marginalized their voice - the marginalized voice speaking up for the powers that be (and the irony still isn't done).
It is actually easy to see why they would react that way. It is exactly what they wish, on some level, someone would have done for them when their voices had been marginalized and it does seem to be the loving thing to do.... and it is, for awhile. There is a point, however, when it should be clear that, while some have chosen to be a part of the change, others do not have ears to hear and out of love for the overall Body of Christ (of which they are a part) we must shake the dirt off of our collective feet and continue on our journey forward. While we do, we can still wish blessings upon them, but in a time when transformation is essential for the longevity of the Church, holding our forward movement back for those who have made it clear they do not have ears to hear is analogous to shooting the Body of Christ in the foot.
Ironically, there will be Left Behinders that chose to remain behind. They will act as an anchor pulling the Body backwards as it tries to move forward. The funny thing is, if we don't move forward we will continue to move on that tangent further and further away from God's will and when the second coming does arrive, at least in terms of their own theology, we will all be left behind...even them.