When Christian men hear or read about the virtue of gentleness, they often substitute this virtue with the vice of niceness. This is especially the case for younger Christian men, and the results can be deadly when it comes to love, marriage and fatherhood.
What is niceness? Niceness in many ways is a perverted form of gentleness. What does true gentleness look like? Genuine gentleness brings needed force into a situation or relationship, but it is a force that is moderate and kind in its presentation. Gentleness is respectful, but respectful enough to be truthful and at the same time gracious. 
Niceness is often disguised as gentleness, but you can see the difference if you look closely. Mere "niceness" brings no redemptive power to a matter at hand, whether with a spouse, co-worker, or obnoxious coach who belittles and exasperates a child. The apostle Paul admonishes fathers not to exasperate their children (Ephesians 6:4). Christian men who focus on niceness try hard to fulfill this requirement but in many situations fail since a father's lack of power frustrates and angers his children. Nice Christian men also fail to stop other fathers from exasperating their children because correcting another, may seem, well, not very nice. Due in part to their spiritual training, nice Christian men often double-exasperate children.
In many ways, the unstated goal of niceness is to say or do something without saying or doing anything truly meaningful. It favors manners over truth. Niceness is the drowning of force, the unwilling to use any. It is the state of being that has been defined for ages as "weak." 
The understanding that a gentle man still wields force - albeit moderately - and with it power, is an eye-opening revelation to many of the Christian men at my conferences. Their spiritual training has them believing that gentleness means using no force at all - like niceness. This revelation often propels them into a better, though uncharted, direction.

When Is It Okay to be Forceful?
Learning to use the appropriate amount of force in any given situation takes time and a cultivation of virtue. Yes, the moderate use of force for redemptive purposes is a virtue, but please understand that it can also be a vice. Some situations in life demand setting aside even gentleness, requiring more than moderate levels of force. For example, a police officer who only uses moderate force may be a dangerous imposter when greater force is necessary to ensure peace and protection. By the way, if you trace the origin of the word virtue, as Dr. Henry Cloud has in his beneficial work Integrity, you'll see that one of its meanings is "force." Virtue brings energy and force to a situation. Niceness refuses the task, usually because of fear of rejection.
A man's need to cultivate virtue brings us to another point: If the goal of Christian life is to imitate Jesus, then it's important we have an accurate picture of Jesus. It's important we knock down, whenever possible, the anti-biblical and false idol of Pleasant and Mild Jesus, who we foolishly try to emulate. True, Jesus was gentle. But he was not always gentle, thank God. Moderate force cannot save us from wickedness, evil, addictions, the devious plans of others, or our own convenient rationalizations that bring numbing comfort but not true security. Sometimes the best thing a good person, or God, can do for us is to give the gift of desperation--something gentleness is ill-equipped to perform and something niceness never does. 
I receive many letters from wives of Christian Nice Guys, explaining how heroic they've behaved in order to help their husbands be more involved, connected, and protective of their families. Yet no change has occurred. Sometimes the gift of desperation is the only option that works.