The Kingdom intersects the Sermon on the Mount; I have written about this topic before, so I won’t reiterate the same points, but after reading The Sojourner Chronicles, Buddy Overman is spot on. He critiques a recent article from World Magazine written by Anthony Bradley. He notes that Bradley’s argument is that some of the new reformers, like David Platt and Acts 29 churches, are pressing a “Radical Christianity” and “New Legalism” on the church, to which Overman refutes with some credible points. Driving to the gym this morning, I heard the same blast of questioning against Francis Chan, a man who I respect. There is a bigger push it seems to maintain grace covers everything, than exposing sin and striving for truth.
I see the danger not in radicalism or legalism, to which men like David Platt steer well clear of and other Acts 29 pastors, but in antinomianism. Fancy word right? If we break it down, it makes perfect sense; the word anti or against, and the Latin nomos, meaning law (here’s a good link for deeper biblical study on the issue). Views like Bradley’s can be dangerous, in that if the believer denounces the holiness aspect, he/she may jeopardize the Gospel’s power of grace. Quite honestly, the “grace covers everything” argument was made in the first century and Paul vehemently affirmed that while there is forgiveness through Christ, there are still consequences for sin.
Downgrading the definition of doulos, to which Paul and Peter describe themselves in their letters to the churches, the Greek word for bondservant or slave, is a major dilemma in Americanized Christianity. While pastors as I, will teach God’s forgiveness of sin through the grace and blood of Christ and that as a free gift, obedience must be part of the equation, not in salvation, but in Christian ethics and walk. Integrity matters!
Therefore, antonomianism becomes a legalism in and of itself, this danger is far worse because it serves as a false guide for the believer to relax in his/her own understanding and not on the holiness and rightful Kingship of Christ—namely that He purchased the believer—He is outright owner.  
In my opinion, there is no fear of radical legalism in the new reformed churches, for the reasons of grace; they get it. Charles Hodge sums it up:

“Antinomianism has never had any hold in the churches of the Reformation. There is no legal connection between the neglect of moral duties, and the system which teaches that Christ is a Saviour as well from the powers as from the penalty of sin…”[1]

While one may argue that this was Bradley’s idea in noting radical Christianity and new legalism, his dilemma rests in the underpinnings of lawlessness. Paul stated that Christians do live by the law—the law of faith (Rom.3:27). This means that our walk must match our profession—I realize, this is hard, difficult, seemingly impossible at times, but as Overman correctly points out “it is self-evident that Jesus’ call on each of our lives is a radical missional call of faith—one that requires radical self-denial, radical allegiance, radical public faith, and a radical pursuit of reaching the lost.”
Therefore, I stand with Overman, we must be radical and missional.
[1] Hodge, Charles. Systematic Theology, Vol. III. (Peabody, MA: Hendrickson, 2003). 241.