I would like to propose that we stop worrying about (imaginary) ideological classifications and rather focus on what people are doing, what action they are or aren't undertaking. Palestinians are being driven from their land and murdered by Israel. The only serious question is how do we prevent this action. In other words, what are WE doing wrong? But I would urge that this is true in every case. Of course blind adherence to a creed backed by strong sentiment is bad, and this is true not just of nominal religions but other faiths as well--atheist Marxism, e.g. Since we all are prepared to face facts cooly, debunking is for not required and, in my opinion, a waste of valuable time.
So what if you're confronted with a fanatic? Then show him or her the facts, perhaps supplemented with a little theory or philosophy sprinkled on top. In my experience this works oftener than you might imagine, but if it doesn't then there's nothing more you can do anyway. You just have to move on--besides, they could be correct.
My conclusion: try to avoid what Norman Finkelstein calls "intellectualizing"--if you must intellectualize, then be sure to define your terms clearly and stick to your definition (think about what you mean when you say 'religious', e.g. NB: reading analytic philosophy can help!)--and direct everything you argue toward a concrete objective, one that you comprehend clearly. Or: think about what's wrong not with his beliefs, or even his actions, but what is wrong with MY actions?**
*A true of false statement irrespective of Mamet's apologetics re: Israel, although I admit the irony of quoting him in this context.
**Like everyone else you have "the right" beliefs, this is a given. And true beliefs can be change by will even if you wanted them to.