Change "God" to "hell".
Right now your groups focus is on disproving god, as you have made it not only your staple argument and logo, it seems you even have classified people into those two categories, those who beleive and those who dont. This is a grave mistake on your part, because you alienate, and you isolate, and you put yourself against more people then you truly wish to go against. It also weakens your arguments, because there is truly a plethora of reasonable conjectures to prove of "god", especially in other global religions, that even transcend the laws of your science. You cannot prove nor disprove, so you have just rested on your laurels that all who do believe make god out to be "pixie dust floating in the sky" (as one of the members here calls it) and other equally improbable mythological hypotheses'. Rather, the source of the hatred, and the militaristic convictions in Christians lie not in their faith in God, but in their faith in Hell. That Hell is the place prepared for gods eternal punishment. This is their conviction that seperates them from treating others as equals, such as you guys. Furthermore - the concept of hell is of such tremendous preposterous proportions, that you can create some intense and very self-evidencing conjectures against hell, so much that they will not be able to stand on a foot. The concept of "hell" is so tragically limited, and has a hundred thousand paradoxical loopholes in the reality of "existence". If you changed your word "God" to "hell", you would garner the attention that is NEEDING to be addressed to these communities of fanatical Christians. Civilizations that tremble in their frightenednous to fear, will tremble in their frightenednous to truth - as you give them truths that even they cant refute to themselves, then they will embark on a journey of further discovery, and come to the realization of what IS self evident.
It takes no intellectual capacity to realize the insanely impossible reality of hell, an elementary student could easily understand, it takes someone to be honest with their selves. So, when you talk to an evangelist, ask them the right questions - make them think about their own faith, challenge them, and help them to see. So long as you keep sticking to "does God exist" or "does Jesus exist" or "is Jesus the son of god" and so on, you are just scratching the surface of their own lies, the root of their own lies is attached to their own inner trembling to their fear of death - and if exploited and observed, and you can transmit a solid conjecture to them, they cannot help but to ask themselves, and hopefully, they will see.
However, you do run into some problems here, sometimes, just by simply pointing out the truth of ones own concepts, they become more scared, and they react by getting angry, to become outwardly hostile, as if to fight the truth away, some of them will fight truth like they fight for their life. Because to them, they are fighting for their life.
A philosopher once said, "many men live life in constant trembling, trembling from their own fear of death, and they run away from it and indulge their selves in efforts to appease the trembling, but underneath those superficial indulgences, lie that trembling, which remains ever present in them." This is true for the ordinary mind, but the strong of mind has conquered the fear of death, not by rationalizing it, but by facing death head on, and becoming one with it, not physically, but to give your self to death. This dissolves the human identity, or ego - but once it is realized, you will see that all things associated with your ego, never truly existed in reality, they were purely illusions. You can disillude people, but some people take it one step at a time, I promise you, your pursuits into opposing Christian fanatics will not lie in "prove god", but in pursuing reasoned inquiry into the concept of hell, and assessing and critiqing the book of revelations.