The following is an excerpt from Chapter 1 of my book, "Apikorsus!"
There's a story that often gets repeated when the subject of apikorsus comes up. It usually goes something like this:
An apikores moved to town, and the rabbi visited to welcome him. They talked for a while, and the rabbi asked if the newcomer would come with him to mincha.
"Thank you for the invitation," the apikores said, "But I'm an atheist."
"Really!" The rabbi said. "I've never met an atheist before. I'd love to get your perspective on the daf I'm learning."
"You don't understand." The apikores said. "I'm an atheist. I don't learn gemara."
"I see." The rabbi said. "But I assume you've learned through mishnayos. I'm in the middle of…"
The apikores shook his head.
"No?" The rabbi said. "Well, you must have a good understanding of Tanach, the foundation of Judaism, with the meforshim. After all, you've concluded that they're all wrong! Perhaps we could discuss this week's parsha."
The apikores shook his head again. "Rabbi, I'm an atheist. I don't do any of that religious stuff."
"How could you have rejected Judaism?" The rabbi asked. "To reject Judaism, you first have to be a scholar. You haven't studied anything. You're not an atheist, you're an ignoramus."
The story is told to make the point that one must be thoroughly acquainted with Judaism before he is qualified to reject it. The apikores in the story is not qualified to reject Judaism. Instead, he's just a fool, talking about things he knows nothing about.
Some people expand on the theme, like one rebbe who told his class, "Ask the apikores. Did you ever read Aristotle? Plato? Moreh nevuchim? No? Then tell him you are not an atheist. You are an am haaretz (an ignoramus)."
There are several problems with the premise of the story. The first is that it often is not true. Most people who go OTD have spent years in yeshiva or Beis Yaakov. They have studied gemara, mishnayos, Tanach, and more. Many have also read Aristotle, Plato, Moreh Nevuchim, and other philosophers, and are often better versed in theology than the average believer.
The third problem is that the rabbi doesn't hold himself to the same standard he requires of the apikores. …
The story can be told equally well the other way around:
There was a frumme yid who moved to a college town. Word of his presence spread, and the dean of the college was intrigued. He arranged a meeting with the newcomer.
"I've never met a true believer before." The dean said. "Is it true that you're a maamin, that you really believe that the Torah was written by an All-Powerful God Who created the world and gave the Torah to the Jewish people at Sinai?
"Absolutely!" The yid replied.
"Great!" The dean said. "I have some questions I was hoping you could answer. How do you account for the similarities between the Torah and Ancient Near Eastern mythology?"
"Mythology?" The frum man said. "That's avodah zara! I don't study that."
"I see." The dean said, "We'll avoid that subject. How do you account for the literary evidence that the Torah is a composite work?"
"That's kefirah!" The yid answered. "Chas v'shalom that I should ever think the Torah might have been written by humans!"
"What can we talk about, then?" The dean asked. "How myths develop? Archeological evidence for the origins of the Jewish people and for the beliefs of the early Israelites? Geological evidence for the age of the Earth? Cosmological evidence for the age of the universe? Biological evidence of evolution? The philosophical problems with proofs for the existence of God? The history of the development of Judaism, and the many different forms it's taken over the millennia? Influences on Judaism from other cultures?"
"None of those! "The frum man answered. "Philosophy is foolishness, and the scientists and academics are either lying, or their findings are distorted by the mabul."
The dean stood up. "Thank you for meeting with me, but I see we have nothing to discuss. To really be a true believer, you have to at least be educated enough to understand the problems with believing in God and Orthodox Judaism. You're not a maamin, you're an ignoramus."
 Margolese, F. (2005). Off the Derech. Jerusalem, Israel: Devora Publishing Company. P. 178