(Image courtesy of http://www.christianitytoday.com.)
"Finding the common ground" is a phrase that makes me cringe because it seems to allude to making compromises and being fearful; yet, this is not always the case.  Finding the common ground can be beneficial; for instance, if you are trying to barter with an individual, it is helpful to find a common price on which to agree.  Furthermore, compromises are not always bad.  Sometimes a husband and wife will need to compromise on their household chores; for example, "I'll make supper if you do the dishes."

Finding the common ground, however, when it comes to truth and principle can be dangerous - which is why the phrase scares me.  Finding the common ground is never a reason to abandon truth and principle solely for the sake of "peace," but it is helpful in starting the conversation about truth and principle.

In the days of the early church, the Gentiles (anyone who was not a Jew) grew increasingly hostile toward both Jews and Christians.  Jews and early Christians were even called "atheists" by the Romans, who observed that Jews and Christians worshipped one God and not their numerous Roman gods.  This led them to self-justified hatred and condemnation of Jews and Christians.  For these reasons and others, Jews and Christians were persecuted heavily (Christian History Made Easy, Timothy Paul Jones).

There was a Christian man named Justin, however, who believed the best way to reach the Gentiles was through finding the common ground.  He saw, for instance, that the Gentiles worshipped gods.  He saw, too, that Christians worshipped God.  The common ground was obvious: "we are all worshipping deity."  Thus, Justin would engage in conversations with Gentiles regarding the common ground, and then proclaim the truth of God as the reason for all humans worship of deity (Christian History Made Easy, Timothy Paul Jones).

In today's context, Justin might have engaged in a conversation with a supporter of homosexual union in this way: "I see you hold marriage as a valuable relationship.  So do I.  And so does God.  In fact, it is God who institutes marriage and holds this union in high regard.  Since God created all of us, this is the reason why we both value marriage."  Using this common ground, Justin would then go on to engage in conversation (both listening and speaking, mind you) about the truth of marriage as God created it.

This early Christian was soon martyred for his faith and is known best today as Justin Martyr.  The truth, then, even when presented in the humblest of ways, is no guarantee for acceptance.  This is because it is God who owns salvation, not man.  Man has a responsibility to bear witness to the truth - to inform the mind - but it is the Lord God who changes men's hearts.

Justin Martyr was not alone in his method of preaching the truth of God in this humble manner.  The apostle Paul, in Acts 17, engages the Gentile community in Athens in a similar way.
"Men of Athens!  I see that in every way you are very religious.  For as I walked around and looked carefully at your objects of worship, I even found an altar with this inscription: TO AN UNKNOWN GOD.  Now what you worship as something unknown I am going to proclaim to you.
The God who made the world and everything in it is the Lord of heaven and earth and does not live in temples built by hands.  And He is not served by human hands, as if He needed anything, because He Himself gives all men life and breath and everything else. 
From one man He made every nation of men, that they should inhabit the whole earth; and He determined the times set for them and the exact places where they should live.  God did this so that men would seek Him and perhaps reach out for Him and find Him, though He is not far from each of one of us.  'For in Him we live and move and have our being.'  As some of your own poets have said, 'We are His offspring.' 
Therefore, since we are God's offspring, we should not think that the divine being is like gold or silver or stone - an image made by man's design and skill.  In the past God overlooked such ignorance, but now He commands all people everywhere to repent.  Fore He has set a day when He will judge the world with justice by the Man He has appointed.  He has given proof of this to all men by raising Him from the dead" (Acts 17:22b-31).
Even after Paul's proclamation of the truth, built upon their Greek practices of worship to an unknown god, only some of them received Christ while others were angry and hateful toward him.  The Gospel is salvation for all who would receive it, but condemnation for all who would reject it.  Yet salvation belongs to the Lord, who alone can turn hardened hearts toward Him; it is our task, as servants, to preach the Word.

If any encouragement can be taken from the life of Justin and Paul, let it be that we serve an awesome, holy, powerful God who is worth even dying for!  And let our wits be sharp and our minds wise as we engage a hostile world with the truth that sets men free!

Lord, give us wisdom and courage to engage the world around us.  Let us speak the truth of Your great salvation to this dying world, full of sin because all men are slaves to sin.  Please help us live courageously, dear God.  Amen.

"Eighty-six years have I served God, and He never once wronged me; how then shall I blaspheme my King, Who has saved me?" (the words of Polycarp before he was burned alive at Smyrna).