You cannot disprove the existence of God any more than anyone can prove it. It is a belief. Asking someone to prove something that is by definition un-provable is pathetic.
You are correct in that the concept of God by definition cannot be demonstrated. That means, without qualification, that it is fiction, or as related to reality, false. You are the first Christian I have seen on these forums that has so succinctly agreed to that. No, actually I have also seen very few atheists or agnostics able to understand that so clearly too. Regarding belief though, God is not a belief, it's a concept that some may believe in or not. You agree it's not real by definition, but hold that belief IN SPITE of that fact. This is very the definition of Faith, and you have faith. Belief without or in spite of evidence (generally, in this case evidence is the acceptance that it's by definition not real) = faith.
To Christianity though, doesn't it teach that non-believers are sinners and will burn for eternity in hell? That's by definition, teaching discrimination as a core belief. Discrimination in itself is not bad though, it's natural. But discriminating against those not of your religious belief, when it goes beyond just a private belief, and affects others, especially in matters of law, politics, education, healthcare, etc., is wrong. Its OK to be wrong sometimes, but let's not claim that those who oppose Christianity because Christianity is in bad ways, discriminatory, are then labeled as "discriminatory" and it's a moot point. It's not a moot point. Remember that Christian beliefs have infiltrated laws, and those laws affect non-Christians, often in very big life changing ways. There is cause for concern and opposition, let's not act like it's all just private belief in private churches (who are somehow tax exempt to boot).
Also, someone who kills someone is a killer. But if you were legitimately defending yourself against a home invader at night, I can assure you being that sort of "killer" is quite different than being who breaks in and kills home owners to steal their things. Both look in the mirror and have killed, yet you and I both know they are different, and one my be justified, and one is not. Just because someone discriminates against Christianity, doesn't mean they are hypocritical or "two wrongs don't make a right". Go one level deeper as to WHY the behavior was engaged in, and there you may find good vs bad.