This is a mistake that you don’t have to be an apologist to make. Every Christian stumbles on this at some point. Whatever your role, never, ever do this:
Do not assume what another person believes.
This happens so often. The Christian thinks they are impressing the person with their knowledge but really they are just shutting down the conversation. Here are some examples of what this looks like.
A Christian talks to a Mormon and tells them that they are attempting to become a god. The Mormon denies it and the Christian accuses them of being dishonest. What is the mistake here? There are Mormon writers who have taught, “As we are, God once was. As God is, we will one day be.” There are Mormons today who believe that. But not every Mormon believes that and many Mormons do not even know about that doctrine.
A Christian talks to a Muslim and tells them that they agree with terrorists and that they want all non-Muslims killed. The Muslim denies it and argues that they see Jihad as a spiritual struggle. The Christian has read enough books and websites not to believe that. What is the truth? There are Muslims who have a violent vision of Jihad and Muslims who have a spiritual vision of Jihad. Just because a Christian is angry at terrorist attacks and has read from an apologetics website, does not mean they know what a particular Muslim believes.
A Christian talks to an atheist and tells them that since they do not have an objective moral framework, they see the holocaust as no different from baking brownies. While it is true that if there is no objective morality, there is no basis to determine what is absolutely right or wrong, it is not true that atheists take things like the holocaust lightly. Atheists are just as outraged by injustice and violence against innocents as anyone else, including Christians.
So if we can not make assumptions about beliefs after studying a worldview, what do we do?
The best thing a Christian can do is to talk to the person, ask questions and listen. This is actually a lot of fun and you will learn so much. The exciting thing is that not only will you get a better understanding of what they believe, you will also be building your relationship with them. If you listen to them, they will more likely listen to you.
What about all those apologetics books, websites and workshops? It is still important to read and learn from sources outside the worldview you are studying. These resources will give you the vocabulary and the framework to work within. But let the individual tell you what they believe. After all, you don’t want someone else telling you what you believe based on what they read on an atheist website.