Attacks against theism come from multiple sources. Yes, the hypocrisy of the Christian world is a witness against us; it just isn’t the only witness against us. There are also attacks from science, from philosophy, from history/archeology etc. And each of these deserve a response. Our failure in one respect is not an excuse to also fail in every respect but to try to do better in all.
As far as debating under a reductionist view, I will let you elaborate a bit further before responding. But, if I am understanding you correctly, accepting a reductionist view for the duration of a debate does not mean we have to accept it wholly or that we will lose the debate.