It doesn't mean you are wrong. It means you don't have an answer. Go study and get an answer and get back to him. Stating that Atheism is a religion Atheists will repeatedly tell you that they are not in a religion. A religion almost always is defined to include belief in a deity of some sort.
Atheism is non-belief in a deity.
To label an atheist as a religious person is to put up a roadblock to any effective communication. The Christian would simply role his eyes and think that the person doesn't know what he's talking about. No one has all documentation for everything they say. It is not reasonable to require proof from an atheist on everything said. It adds an air of credibility to your argument.