I'd explain it like this: I'm not against the members of the people's temple, I'm against Jim Jones.
The JW conflation of god with the watchtower is seemingly pretty universal. I told my father that I could no longer conscientiously support the watchtower society in any way, and his immediate response was "we all have to prove to ourselves that Jehovah is real." I'd said nothing about Jehovah, but that was his immediate reaction. You're going to have trouble creating a distinction between the cult and their god in the mind of any JW, no matter what you say.