In my research for my Church History and History of Mission curricula (for teaching at Turkana Bible Training Institute and Mission Institute East Africa, respectively), I ran across this gem from Claudius Buchanan.  He was addressing a meeting of the Church Missionary Society on January 7, 1814.  The famous William Wilberforce was one of the speakers at the meeting.  Dr Buchanan’s style  may seem a bit old-fashioned now, but give it a listen:

“In your endeavours to convert the heathen, let your address be ever characterised by the meekness of wisdom (James iii. 13).  Address them not in too impassioned a manner while they yet continue in an unconverted state.  They will not understand you.  They will not themselves be in the least affected by your vehemence, and will consider the use of it as a kind of intemperance or folly on your part.  They cannot always perceive the truth of your arguments, but they will understand your courtesy of manners and can admire the beauty of Christian conduct.”

~ quoted by Charles Hole, The Early History of the Church Missionary Society:
for Africa and the East to the end of A.D. 1814 (London:  CMS, 1896), 420.