I posted this on Quora some time ago, mostly I find the question ‘Why is religious conversion wrong?‘ wrong. It is not wrong. But there are problems with the practice that many of us, in our all-religions-are-same enthusiasm, ignore.
There is nothing wrong with a person changing religion of his own free will because he or she found something in another religion that resonated with him/her. Such decisions should be based on one’s own world view and spiritual needs. But that is not how it happens all the time.
I guess the most significant reason behind people’s opposition to religious conversion is the message that the act of conversion sends out. When a missionary pushes someone to convert to a religion, what he or she is actually saying is this:
“I bring you the truth. What you believed in till now is wrong and if you continue to believe in the ways of your ancestor, you will burn in hell for all eternity. Only my religion is right and only my religion can save you from eternal punishment. You should forsake all that you hold dear — your ways, your history, your culture — and you should become like I am. I am doing this only for your own good.”
This is hardly ever said this explicitly these days, but the underlying sentiment behind conversion remains the same. The whole soul harvesting thing reduces religion to a numbers game. The club with the most members wins the game. Often enough, religious conversion is nothing more than cultural imperialism.
The urge to convert roots from the belief that the converted are wrong and the converter knows things the converted do not. This is almost never the case. Many times, the missionary has absolutely no idea what he is destroying. Take the Australian aborigine or the African tribes for example.