I completely disagreed with that statement and I told him why. I gave him a reason. Here are a few:
To be balanced is not to have half of your house on sand, and half on the rock. "It's balanced!" No, it's a major architectural flaw, and the house is highly unstable. If half of the house collapses, the other half is no longer suitable for residency. The whole house is ruined by half a collapse. It's the most balanced to be completely on the rock.
In the same way, you can imagine three men: one man jumps wholly into the support-less air of The World, the second stands firmly upon the rock of Christ, and the third tries to balance- on foot on both. You cannot balance with half of your body weight hanging over the edge with all the force of gravity (your desire to sin) pulling you down and expect to survive. You will fall, and you will die.
2) God does not recognize either the house built half-way nor the man balancing on the edge. He only recognizes two alternatives: you're either for Him, or you're against Him. "He who is not against us is for us." (Mk 9:40, Lk 9:50) and "You cannot drink the cup of the Lord and the cup of demons too; you cannot have a part in both the Lord's table and the table of demons." (1 Cor 10:21). Logic demands this be so; either Christ has died for you, or He has not. Either you belong to Him, or you do not. Either you love Him, or you do not. Either you stand upon Him and wish to do so, or you stand upon thin air and desire to separate yourself from the Christ in scriptures (although perhaps not your imaginary Jesus). So the appeal to "have one foot in Christ and one foot in the world" is really illogical and impossible.
3) Christ demands complete obedience, not half-way lukewarmness. Christ once spoke to the church of Laodicea, saying: "How I wish you were either cold or hot. But as it is, you are neither! Therefore, I shall vomit you out of my mouth." (Rev 3). He also says, "Sell your possessions and give to the poor." and "He who loves: his mom, dad, sister, brother, son, daughter, possessions, wealth, or even his own life more than me is not worthy of me."
Christ does not demand some stupid, illogical, half-way balancing. He wants you to suck it up, be mature, and choose. And for you men, he wants you to be a man and choose the way of outward suffering. Be a man, die to yourself, pick up your cross and follow Christ into joy unspeakable.