Q: Is the topic of origins important when witnessing to non-Christians?
A: It’s absolutely important to understand that evolution is one of the biggest stumbling blocks to the gospel of Jesus Christ.
When Ken Ham visited Edinburgh, Scotland, a number of university students came up after he had given a lecture on creation and said, “We suddenly realized something tonight. When we’re trying to witness to non-Christians at the university, they always bring up the same two questions.”
Ken stopped them and said, “I can tell you what those two questions are about: creation/evolution and death and suffering.”
“Yes,” they said, in surprise, “they’re the two that come up over and over again. But we’ve been told by our churches to ignore those questions and just tell them about Jesus dying for their sins on the Cross.”
Then they said, “What you’re telling us is that we need to deal with those questions to show that we can give answers for what we believe. We need to show them that evolution is not a proven fact, so they will listen when we talk about the gospel message.”
Precisely. We need to answer these “stumbling block” questions in order to witness effectively to non-Christians.
I got this in an email, and I sure wish I could post a reference, but it didn't have one. Answers in Genesis is the best source I can offer, and there you will find more by Ken Ham, who is, in my opinion, an excellent speaker/author.