The sanctification argument for refusing to listen to certain Christian apologists

Here is an argument I posted at another forum.  I argue that despite the fact that many bible scholars are consistently Christian in their faith, their unwillingness to break fellowship with other Christians they know are living in sin, proves that such scholars probably aren't true Christians to begin with.  The internet allows Christians who live in the sin of slander/reviling to run wild with little to zero chance that their local pastor, will ever know, and when the pastor is told, he typically brushes this off without employing the admittedly emotionally difficult disciplinary measures required in Matthew 18 and 1st Corinthians 5:9-13
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In my experience, while some Christian might have a lot of knowledge of bible scholarship, they are often shockingly lacking in sanctification.  I've known really smart Christians who are routine drunks, really smart Christians who routinely engage in pre-marital fornication, etc.  God only knows how many Christian "internet apologists" there are who download pornography while posting defenses of biblical inerrancy to debate forums.

The problem is bigger than just the Christians who "live in sin" as we typically use that phrase.  The problem includes Christian scholars and leaders who exhibit zero motive to fulfill the harder parts of the bible, like obeying Matthew 18 and excommunicating the so-called "brother" who refuses to repent of some sin committed against another. 

For example, many "internet apologists" routinely hurl insults at whoever they are debating.  Apostle Paul told Christians to stop communicating with so-called Christian "brothers" who constantly "revile" other people:

  9 I wrote you in my letter not to associate with immoral people; 10 I did not at all mean with the immoral people of this world, or with the covetous and swindlers, or with idolaters, for then you would have to go out of the world. 11 But actually, I wrote to you not to associate with any so-called brother if he is an immoral person, or covetous, or an idolater, or a reviler, or a drunkard, or a swindler-- not even to eat with such a one. 12 For what have I to do with judging outsiders? Do you not judge those who are within the church? 13 But those who are outside, God judges. REMOVE THE WICKED MAN FROM AMONG YOURSELVES. (1 Cor. 5:9-13 NAU)

But how good are the odds that any such sinful Christian's pastor knows about this, and can therefore implement this biblically necessary discipline?

I've witnessed plenty of cases where well-known conservative christian scholars became knowledgeable that one of the Christians they fellowship with routinely "reviles" everybody including other Christians, using language that is in clear violation of Ephesians 5:4 and Colossians 3:8...but these scholars did precisely nothing to address it.  They simply never attempted the least bit of biblical response.

How long can a Christian scholar turn away from the more demanding morals the bible requires of him, before the skeptics can be justified to say such scholar is likely lacking in sanctification?  Does 1st Corinthians 5:11 place a burden upon all Christians, or only on local pastors?

I'd like to know what the Christians here would think of the skeptical argument that says a Christian can be safely deemed to lack salvation, if despite a scholarly-level knowledge of the bible, they carefully refrain from addressing issues of sin in their own lives, or in the lives of other Christians whom they regularly fellowship with.

I'm not saying nobody can be a Christian unless they are sinless.

I'm saying the more you disobey the biblical requirement to reprove sinful brothers and disfellowship the unrepentant, the more the outsider is justified to conclude your lack of sanctification testifies to your lack of salvation. 

Sure, the the bible will allow for the husband who commits adultery to still be a Christian.

But does the bible allow a husband to be a Christian if he has been committing adultery every day of the week for the last 20 years?

So the ultimate question is:  even if the skeptical attack is not infallible, can the attack still be "reasonable" in concluding that where Christian scholars either live constantly in sin, or sheepishly run away from a need to rebuke a sinful brother, this lack of evidence of sanctification increases the odds such Christians are not authentically born again?