I guess I am thinking that if there is a grand disservice that some brands of Christianity have done to the advancement of the Kingdom, it is the narrowing of what it means to have a knowledge of Christ. I often find myself on a tightrope between two sides because I do actually believe Christ to be supreme; I believe that Christ is the Light that every being will stand before on the last day. But I also believe that the spark of Christ has existed in every human being since the start of time (inasmuch as they have a knowledge of God), and many humans know that Light very well without knowing the name of Christ (as well as those who claim the name but reject the Light). In fact, historically the "Christian" church may have done as much to obscure the true light as reveal it. Frankly, I too have rejected the "Christ" that was presented to me much of my life. But the Light of Christ, of the goodness, kindness, and truth of Christ, is something resident in each person that can be turned toward or turned from.
Anyway, here is Lewis from Mere Christianity:
...But there is another way of demanding results in which the outer world may be quite illogical. They may demand not merely that each man�s life should improve if he becomes a Christian: they may also demand before they believe in Christianity that they should see they whole world neatly divided into two camps � Christian and non-Christian � and that all the people in the first camp at any given moment should be obviously nicer than all the people in the second. This is unreasonable on several grounds.
(I) In the first place the situation in the actual world is much more complicated than that. The world does not consist of 100 percent Christians and 100 percent non-Christians. There are people (a great many of them) who are slowly ceasing to be Christians but who still call themselves by that name: some of them are clergymen. There are other people who are slowly becoming Christians though they do not yet call themselves so. There are people who do not accept the full Christian doctrine about Christ but who are strongly attracted by Him that they are His in a much deeper sense than they themselves understand. There are people in other religions who are being led by God�s secret influence to concentrate on those parts of their religion which are in agreement with Christianity, and who thus belong to Christ without knowing it. For example, a Buddhist of goodwill may be led to concentrate more and more on the Buddhist teaching about mercy and to leave in the background (though he might still say he believed) the Buddhist teaching on certain other points. Many of the good Pagans long before Christs birth may have been in this position. And always, of course, there are a great many people who are just confused in mind and have a lot of inconsistent beliefs all jumbled up together. Consequently, it is not much use trying to make judgements about Christians and non-Christians in the mass...
That sounds a lot like Romans 2. And 1 John 4.