An "antimissionary" or "counter-missionary" is one who believes that religious-supremacy should be countered in a like manner to other supremacist ideologies. A missionary is one who believes that all different cultures and religions must be dismantled and destroyed in favor of a supreme religion. An antimissionary is one who disagrees, and counters by advocating for toleration and understanding. One of the most vocal antimissionary groups is Jews for Judaism whose name is a parody of the evangelical, religious-supremacist, Christian group Jews for Jesus.
Peter: I really wish antimissionaries would stop persecuting me when I'm evangelizing!
Avi: How are they persecuting you?
Peter: Whenever I advocate for the absolute destruction of other faiths and cultures in favor of my own faith and culture, they always object!
Avi: Maybe you should stop advocating for the destruction of other faiths and cultures, and learn to live in peace...
Peter: Avi! You sound just like an antimissionary! Stop persecuting me by denying my right to persecute others!