That article says that the government was forcing the Karens to convert to Buddhism.
And who did they send in? (300 Buddhist monks) That's at least of the level of a "military draft"; or are you going to excuse the German soldiers who were "drafted" in WWII and only blame the Nazi leaders?
And BTW. I'll betcha somebody spending some time digging will find a whole lot more than 300 Buddhist monks involved in this kind of "dirty work" -- given that almost 30,000 Karen people were targeted. (And my recollection from geography is that the Karen people at one time inhabited a very long strip of North-South land...so they're likely to have been spread out)