I agree. Asking an Atheist for "facts" is the same as asking a Christian for "facts". The Atheist will argue that the "facts" they offer are valid, the same with the Christian. Sure, we can all use the same worn out line of, "It is the Bible, so it is fact." If that HAS to be considered evidence, then the Atheist will say, "Okay, here is my book written by random people that say that God doesn't exist. Most of the time Christians are too stubborn or have that "I am a Christian, so you have to believe me" type of attitude.
So to answer the original question, "Can Atheists prove that Atheism is based on facts?" MY answer: No. But a Christian can't either.