Thanks for the reply, I'm relieved to hear you aren't a Jim Wallis fan. How do you approach someone who professes to be born-again but doesn't display any fruit of the Spirit?
Unfortunately, I get to do this all the time...
Generally, I'll start asking exploratory questions -- issues that would never offend a true believer, but if answered incorrectly point out someone who has their faith and/or trust in something other than the Cross of Christ, as expressed biblically. For instance, "Tell me about the time when you accepted Jesus as your Savior." To a believer, this is generally cause to celebrate the testimony of salvation. To a non-believer (or merely religious person) the answer may be something that has to do with "always being a part of the church" or perhaps "I did this and I did that..." with no real mention of the scriptural mandate to repent and be born again from above.
Sometimes I just "share the gospel in this new way that I've been playing around with..." to gauge response.
What I seldom do is hard-sell the gospel via a bunch of Bible verses. After knocking on over 15,000 doors in my career as a church planter, and sharing my faith with thousands of other people in all sorts of scenarios, I've seldom found the sharing of straight up Bible verses very effective. Generally, a relationship-building conversation can lead to the place where one can mention Scripture, but if the person is un-saved, Scripture is as often a turn off as it is a workable solution. NOTE: That does not mean that I have a low view of Scripture or of the power of the Holy Spirit through the Word. Not at all! The direct revelation of Scripture is the gospel, and the means God chose to use to bring sinners to salvation. But, to the unbeliever, the Scriptures taste like death, and sometimes I want to spend some time with them instead of just shot-gunning the Word at them like some sort of magical talisman. I'll speak scriptural concepts to see the reaction, then go from there.
One other thing... I'm never shocked when sinful people sin. That is sort of what they do, no? When persons who are supposed to be "churched" come out hard and strong against the true Christian witness, that may be a tool that they are using to see if you can pass some sort of test -- to find out if your faith is real or not -- and/or -- to find out if theirs is. People who do that sort of thing are often not set against Christ, but rather against "stuffy" church people, who they see as weird (and rightly so!).
I know that I've sure met some weird dudes (and dude-etts) in church. People I would hardly ever associate with if not for church as a matter of fact. Churchy people seldom get just how weird they can appear to people who are marginal in their faith, and oftentimes it is the church and the stuff one must do to gain admittance, that chases the prospective convert away. Wish it were not so, but after doing a number of church assessments, I've seen this way too often.
Where do all those deacons find the green leisure suits and why do little old ladies have blue hair?
Why does the church insist on singing songs written in the late 1800s or early 1900s instead of something relevant? Why do they insist on playing those hymns badly instead of having quality instrumentalists take care of business? Why do church members fight at business meetings -- don't they love the Lord? These and a ton of other questions come up (or something like them) when I witness to religious persons who do not show fruit in keeping with authentic Christianity.
The bigger question to me is, "How are we going to identify those persons who are merely religiously effected and not truly regenerate?" That is the tougher issue. The Scriptures have some things to say about judging people's salvation (yes, we can inspect fruit), and the "judge not" passage seems to be the only one that people who are not really God's know. I have a couple of answers, but they tend to require overhauling the church as most operate. It takes true and authentic Christian community to get to the heart of the matter and to truly "know" who is and is not a believer, but that community rarely (from my observation) exists in most churches. Everyone shows up on Sunday, puts on their Sunday happy face, and endures the worship service before heading back to the car and whatever vices are practiced for the other 6.5 days of the week. Pastoral or deacon family visits are rare and not really effective (for the most part) and so the church doesn't really even know who is or is not a regenerate member for sure. I know that I've sure been surprised over the years...
Case in point, a dear sweet middle-aged lady who ministered every week at one church I led. Her's was the picture one would find in the encyclopedia under "saved Christian". She taught Sunday school, was the clerk of the church for over 20 years, and never missed a service. Her husband was a scoundrel and a drunk, and she asked prayer for him constantly. From all appearances she was the real deal. Yet, after one sermon where the gospel was shared in a non-conventional way, she realized that she had no testimony of ever coming to Christ at one point in time, and she came forward to ask how to receive Christ. Everyone in the church, including me, was shocked. This could not be! But it was. She humbled herself, prayed and asked Christ to be her Savior and asked to be baptized. If she was the prototypical Christian before, after she was born anew, she was on fire! She glowed with the light of the Spirit and led many a person, including her husband, to Christ. What a difference! Her coming to Christ sparked a mini-revival in the church and we saw multiple other persons coming out and accepting Christ. We led our association in baptism for 2 years after this event, as God used this woman to spark a renewal that we had been praying to see for quite some time.