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Also, I can talk about anything without believing in it. I just know that you guys are wrong about Christianity and Buddhism but I don't need to believe in Christianity to prove it (debate) and I will not post suttas to prove you wrong since that's against The Buddha's teachings.
Yes, of course you can talk about anything without believing it. Everyone has the right to express, wrong or right, true or false.
A person may say, in Islam there are 4 Gods. Two big, 2 small. Another person may say in Christianity, God has 3 daughters. Regardless true, false, honest or dishonest.
But if we want to have a meaningful discussion, to show a correct view, one needs to support it based on the Authentic Scriptures, that originally defines that Religion. So, if a person want to say, what Islam teaches about God, it can only be considered as the correct view of Islam, if it is shown what the Scriptures of Islam says; Quran and authentic Hadith. To say something without backing it up with Scriptures, does not provide a valid evidence. To say, the Mainstream Muslim, say so, or Christian mainstream say, so, is not a scientific way of verification. So, it is fine, if you want to express the Christianity view, without believing it, but you need to back it up with exact Scripture if you want to provide evidence that what you express, is indeed what Christianity teaches originally. I hope this is clear.
Just because some Christian denominations were not majority, does not mean their understanding was wrong, and just because the main streams are majority, does not mean they are right about every interpretation of Bible. The Bible itself is the standard to determine the Christianity.
Jesus never said, just the majority view is correct. He did not say, His teachings belong to those who call themselves Christians. We need to be accurate about our statements, if we like to have a fair and valid discussion.