That's an interesting topic. It does seem as if historically, missionary work has caused nothing but harm. One thing it repeatedly has done is create stigmatised national minorities that are later persecuted. It usually seems to have gone hand-in-hand with colonialism.
But I wonder how far you can take that? What about 'missionary work' that isn't religious, i.e. converting people in a distant community to communism or capitalism or liberalism? You could probably make the same argument about all attempts to spread ideologies.
I'm sure. Missionaries do some good work. I'd want them or anyone to do that good work without the conversion part, but then they probably wouldn't be there in the first place. Gotta get that return on investment I guess.