Hi, Andrew—No, "OK" does not apply to the part of the sentence in bold. It applies only to the first clause. That clause spells out the meaning of "OK" in the context; it is the proposition to which "OK" expresses assent. It's like saying: "I recognize that people don't really want to talk about Vietnam."
Notice that it would be possible to have: "OK, but I can do a movie about the JFK assassination. That way I can slide Vietnam into the conversation." Even in this case, "OK" would not apply to the "but"-clause, which expresses an alternative to that which has been contextually assented to with "OK."