My favorite example of this is a particular sectarian denomination that believes only the new testament. The old testament, they think, no longer applies to them. So - when it says in Ephesians 5:19 "singing and making melody in your heart to the Lord", they take this to literally mean that there are to be NO MUSICAL INSTRUMENTS AT ALL in their church services. Because the old testament, and therefore Psalm 150 is not inspired scripture to them, they do not have the whole Word of God concerning musical instruments. They take this seriously - their church architecture never joins the education building to their sanctuary, because the New Testament never talks about Christian education. I often poke good natured fun at them, wanting to know if their churches contain bathrooms, because the New Testament never makes mention of bathrooms, either! If you never do anything in your church services (or your Christian life) that is not explicitely talked about in the New Testament, you also do not laugh. There is no record of Jesus laughing.
Exclusionists are not limited to this one denomination. More commonly, it is a body of thought that looks suspiciously on any activity not explicitly approved in the Bible. They frown on movies and television. Extreme groups even reject modern technology completely as being too "distracting" and "fleshly". Don't get me wrong, these can be true believers in Christ - and very good people. This is also not a new trend. I recall seeing houses built in the last century where the chairs are hung on the wall - lest somebody use them in a fleshly way, to relax when there was work to be done. It was a work ethic gone insane - based on the idea that "idle hands are working for the devil".
Now, if the Bible does not come right out and say "movies are OK", "dancing is OK", "makeup is OK"- or "Christian rock is OK", you are at a real disadvantage with these people, who will come back with "if the Bible doesn't say it, then don't do it!".
I think a lot of these people are actually insecure, and do not really know the fullness of the Biblical doctrine of blood atonement and salvation by grace. They do not have a healthy fear of the Lord - they are afraid of Him, and dispair of ever attaining "salvation". It boils down to "salvation by works", which is not true salvation. I admire somebody if they abstain from something out of a sincere conviction that it is wrong, but if they think that is how they are saved - they are wrong.
An almost identical "bad idea" is that if it is pleasurable, it must be wrong. I think this is at the heart of much of the Christian rock debate. The need to "play" - to have fun - is a basic need that God, in His wisdom, has given to man as well as many of His animal species. It is the way young people (and young animals) learn about the world around them. Now - I am absolutely certain that any young person you encounter from about the age 10 up is absolutely convinced that they are "adult". The fact is that young people, by their very nature, still like to "play" - to do fun things. So - in comes stodgy old Christian rock critics into a concert or worship setting, and they see the kids having fun - dancing and enjoying the music. These critics have long since settled into comfortable patterns of maturity, and have forgotten how to "play" and have fun. Living in Central Florida as I do - I hereby prescribe an extended visit for every Christian rock critic to our wonderful theme parks! Perhaps if they recapture some of the joy of their own youth, they will not be so quick to judge young people who genuinely enjoy their worship time with the Lord through Christian rock. Stress is a killer, guys. Even adults need the simple pleasure of play. Next time you go to a Christian rock concert with an eye towards criticism - trying getting caught up in the fun - the spirit of worship - that the kids around you have. You will encounter the Lord Jesus Christ through "new songs" in a refreshing and relevant way.
I also prescribe a viewing of the film "Pollyanna" to every Christian rock critic. There is a POWERFUL message about the true nature of Christ contained in the movie. I don't want to spoil it for you, but I will tell you that if you go around constantly looking for the worst in people, you will surely find it. Try looking for the good in people instead. Then get on your knees in repentance for years wasted - just as the minister in the movie (and I) had to do. I was once like you. Not on Christian rock - on innumerable other issues. I have fling cabinets full of dire warnings about cults, pornography, abortion, homosexuality, and the new age movement. All very true, very real problems. I was active against all of them - to the point I had no joy, no happiness in my walk with the Lord. I have had to back off from all of them to persue this and other ministries instead. I am no longer called to minister in those areas. I have submitted to that call.