The problem with the way the word 'theory' is used (I would say, no longer used but should be) is that 'theory' is just not 'fact'. When a theory hits an edge case, the theory is modified. When a 'fact' hits an edge case, the edge case gets ignored.

Case in point: evolution & creationism. Both theories (as in, not recorded history and not repeatable). What do evolutionists do with 'facts' that are unexplainable in their theory? Just read the comments in this article (sad). What I will give creationists is this: they do change their theory (I know, I know - not all of them! but Intelligent Design and other theories are clearly attempts to modify their theory). Of course, then they get labeled as, essentially, 'stupid.' Creationists can put anything under 'it was created that way', but they get blasted for that. Evolutionists, however, change their 'facts' (remember when the earth was only [insert what you were taught here] years old?). And call it 'science'.

And that is why not calling a theory a 'theory' is important. When a theory is not called by its name, it gets called a 'fact'. And we (naturally) deal with facts very differently.

I am NOT saying we shouldn't build on theories, by the way. But that we should build on them as theories. I do agree with you, though, that the way "it's just a theory" has been used is actually just a slur and, if accepted, would prevent any further progress. I, also, despise that lame rhetoric.

And this is why I think what I wrote does change things... it changes which set of assumptions we use. The 'fact' assumptions or the 'theory' assumptions.