What you see is a consequence of entrenched positions. The details of evolutionary theory are in constant flux; particularly so at present, since genomics is rewriting a lot of the more speculative detials of the interrelationships between organisms. However, evolutionists have seen this healthy re-evaluation of the details of evolutionary theory used as an attack on evolution itself, and tend therefore to be wary about such arguments, when they don't come from within biology.
As for 'guided' evolution; science looks for naturalistic explanantions first. We are nowhere near the point where we can say for any system that there is no way this could have evolved (in fact, for most biological systems, we have a fairly good idea how they evolved). People like Behe, who argue that because he can't think of a way for a complex system like a flagellum to have evolved, they must have been designed, are stepping outside of science, which does not give up in the face of uncertainty or insufficient data. Moreover, science, in first considering all naturalistic possibilities before considering other possibilities, is doing what pretty much everyone does all the time. When you lose your keys, at what point to you consider the possibility they have been stolen by a supernatural being?
I know for a fact that they are with the missing socks, probably engaged in something kinky that I don't want to think about.