The Tension of Worldview

I am taking a course right now called "Poverty and Development" at Fuller with Bryant Myers. Brilliant brilliant man. Seriously. It is a wonderful class. But in all of its wonderfulness - it is pissing me off. I don't quite know if I can bite off what he is throwing at me - grasp what he is saying - and walk the tight rope wire of tension he is setting up.
Worldview is something we constantly have to deal with in whatever type of work we do. We first have to deal with whatever type of worldview we come into different situations with, understanding we have been raised and conditioned in certain ways - I think what I think because of the "glasses" I have been given to wear. How much of that is Biblical and how much of it is just the existential influences battling for attention?
Secondly, we deal with the worldview of others we come in contact with. This can range all over the board. In the Eastern world people are far more spiritual then we in the West tend to be. Much of life happenings tend to be spirit related - my child got sick because the spirits were angry, or my family sinned, etc. Whereas we believe it is caused by germs, bacteria, the fact that you were exposed to toxic pollution or picking through garbage. Or in other countries women are not valued as highly as men and using more physical means to force them into submission is not seen as cruel and wrong - it is a matter of cultural worldview.
When entering into these different situations where do you draw the line of changing a cultural worldview or simply speaking the language you are entering into? If a child is sick from picking through trash but a mother won't let him take medication because she believes it is spirit related and the medication will anger the gods how do you then convince the mother?
I tend to lean on the side of honoring culture and worldview - why bring our "better" Western ideas into this beautifully functioning culture thinking we can create systems and fix everything? Why not enter into their own mindset, speak their language, and see if what we have can fit in to their already growing history and story.
But then I see faults with this. I would believe this when it comes to getting a child his or her medication - simply tell a mother the medication has special power to chase away evil spirits - speak a language she will understand. But when it comes to a woman being beaten or abused I am not so comfortable with taking my time, following the traditional worldview and patiently living within the current system - I WANT CHANGE, this is wrong!
So how do you walk this tension? How do you decide when culture wins and when you need to push harder? Is it lying and dishonest if you try and speak a different cultural language you don't necessarily buy into?
And where does God fit into all of this? Our perception of him doesn't always translate easily to these different cultures. We have to create a new language...more on this later.