If Christians are forced by observation and enlightenment to admit non-believers can (and do) live admirable lives, we are also forced to inspect the admirable elements of the unbelieving life. Unbelievers may often adopt their own enlightenment. Whether they know it or not, many unbelievers accept the philosophe of the French Philosophers.
The philosophe of the French in the 18th Century AD has this rationale, in part. They wish to live rationally in accordance with immutable laws that governed the universe. These laws could be discerned at all levels of reality. Natural sciences were their first provenance but they also explored (Greek dominated) metaphysics. Ultimately, the determined reason and logic helped them form the most advanced possible form of religion far above the "revealed religion" of the various religious Holy Books. Paradoxically, the higher form of religion they followed had little need of a god of any kind.
Certainly, the philosophe school needed no personal god intimately involved with human beings. For them and their post-modern descendants any appeal to a personal god is needlessly provocative, as God has the good sense to keep Himself apart from human rational processes.
The Christian Realist feels an intense need to be loyal to God. We believe God is Personal: Immanent and Transcendent, all at once in Time and Eternity. For us it is imperative to find a link between (our) Faith and the rationalist schools dominant in our culture. We do not wish to see God placed in a separate intellectual category, which tends to put faith concerns in isolation from other human concerns.
Simply put, the admirable life of persons outside the Faith puts Rationality (even irrational Rationality) over concerns of the Faith. As our culture once felt it needed God and Church to live admirably, it now needs empirical data and someone impartial to interpret the data.
Alas, no impartial person can be found in the flesh.
So, we are left to persuasion. The hard fact is we have greater difficulty persuading others whose language we do not speak. We believe God's existence is self-evident and look for ways God's existence in creation implies His intimate interaction with Humankind, en masse, and one person at a time. The Post-Modern philosophe looks for a God similar to that of the Greek metaphysician, a god very different from the revealed God of the Holy Scriptures. For them, God may be taken or left alone, but must not be worshiped ever.
The next ED of the BGCT has to understand he cannot spend his time appealing to his constituency. He cannot pander to local prejudices. At the same time he confronts a cooperative set of churches (an oxymoronic explanation at best) more like a parliament or legislature than a denomination, he must also see the greater set of realities confronting his fading organization. The culture he lives in does not get him. He can pull out a number or text and promote product placement as world view but this is failure in itself. He has to get what is going on around him.
Opinions expressed here are mine alone.