It is easy to draw a continuum. Simply state two ends point that differ from each other on at least one aspect, and declare there to be a continuum in between them. This is the salvation of anyone accused of being a black and white thinker [not of the political sort of course].
Why? You can put your black and white positions at either end of the continuum, and then when anyone tries to attack either end, all they get with a successful blow is your moving a tiny bit towards the other side rather than completely over to the other side -- the latter being the normal reaction of a black and white thinker. Further the latter leads to the complete destruction of the black and white thinker's (BAWT) consistent set of beliefs (they tend to try to have these). Instead of fibrillation ing back and forth between the extremes, the BAWT can instead have their position made complex and sophistacated over time as they pick up the successful attacking arguments against the extremes and linger more towards the middle range on the continuum.
And then along comes someone who will successfully draw an end point right in the center of the continuum. A line drawer, if you will. What's the trick here, and why does it hurt the BAWT?
Drawing a line in the middle of the continuum separates the original end points in such a way as to make them unrelated. The typical move is to suggest that they do not in fact have a common aspect - or at least a relevantly common aspect. Take the really boring abortion issue. The pro-lifers draw a line between not-life ------ life at conception, if I have it correct, claiming that there are no relevant commonalities on the earlier side of conception and the later side - relevant being being alive. They strengthen their general position further by saying that the later side of conception shares the commonality of being alive, and choose that point as the beginning of being human.
To fight them, the pro-choicers must not only move the line, but show that there is not that common aspect on the later side of conception. They have to show that the fetus isn't alive until a certian few other things happen. If they move the beginning of hte common aspect, they move the whole continuum of debate.
In this case the debate becomes boring since neither side agrees about the common aspects nor do they agree about the end points. Two BAWTs with paritally overlapping continuums make for a permanent debate. Heh.
The real problem of the end points though is not in drawing a line to befuddle a debating partner, but rather in unfuzzily distinguishing one end of the continuum from the other and then labelling them for further use.