Those old-fashioned Christians

One of the favorite arguments used against Christianity is that we are "old-fashioned." People will say, "Come on, it's time to join the 21st century and leave those antiquated ideas of the Bible behind." The assumption is that society is always getting better and that the latest ideas are always the best ideas.
This was what Karl Marx said of Communism and what Adolf Hitler said of Nazism, but those ideas waned in influence. This is what people said in the hippie culture of the 1960's when so many young people were advocating free sexual love and drugs. Obviously, those ideas did not last. They only left millions of people dead and lives wasted.
C. S. Lewis called it "chronological snobbery" to assume that because something is out of date, that it is discredited. He said we should ask three questions about an "old idea"
1. Why did this idea go out of date?
2. Was the idea ever refuted?
3. If it was refuted, by whom, where and how conclusively?
If a person cannot answer these questions, he has no right to reject an idea just because it's old, or old-fashioned.
I love what Billy Graham said when somebody said he had taken Christianity back 100 years. Referring to the New Testament era, Graham said, "I was hoping to take it back 2,000 years."