You can't be that effective when you can't hear for yourself what they're saying. Unfortunately, this criticism carries little weight for most development organizations. We believe language learning is paramount for effective education, advocacy, and empowerment.
The Language Imperative
We live in a time similar to Jesus when the Roman Empire was able to grasp global dominion politically and economically. Roman success was inseparably tied to the one world language, Greek. Today, Western nations have been able to dominate politically and economically because of the advantages given to them by English.
English is the New Greek
It's not that the use of one language is inherently evil, but it becomes the tool of the dominant power to eliminate the perspective of the poor who either have no access to learning the language, or who refuse to subject their communications to the cultural symbols embodied in the vernacular.
Speaking in Tongues
The sign of Acts 2 and the disciples speaking in various tongues, or languages, was to teach us how important it is that people hear God's agents speak in their own language.
Acts 2:6 "...and they were bewildered, because each one was hearing them speak in his own language."
Learning to Listen
Language learning is difficult and takes time. The learner not only gains vocabulary, but learning the language lends insight into the thought process enculturated into the people who share those verbals symbols.
It completely changes you to hear a person's story in their own language. You can actually hear them.