Frankly I think you're setting up a no-win situation for the missionaries because if they go out and try to meet the spiritual needs along with the physical needs then you say they are taking advantage of the "weakened" state of the recipients to "Sell" them the Bible. But if they instead go out and just do "good physical works" then the accusation could easily become that they are just doing that to build up a sense of indebtedness on the recipients that they could take advantage of later on or even that they do not care about the eternal situation of these people. Now while there may be people/organizations that are being callously calculating, I think your stance does not allow for the fact that from the missionary's perspective they are attempting to save someone from an eternal situation while also helping with a temporal one while undergoing many personal sacrifices and risks to do so. It's a labor of love and concern.
You wouldn't hear that argument from me personally, but yes, I understand where you are coming from. As far as the Missionary's perspective is concerned, I am allowing for and support it often times, despite disagreeing with the priorities of said perspective.