The term "fruit" is a common Bible metaphor. Jesus said that by their fruit you shall know them. Generally, we take the word "fruit" to mean works or actions, either good or bad.
It is particularly noteworthy that Jesus associates fruits or works with judgment on several occasions as do others in the NT (Matt 7:19-20, Matt 25:31-46, Revelation 20:11-12). That the Bible teaches about a judgment according to works is strange given that mankind's salvation, which most equate with escape from judgment, is supposed to be unrelated to works (Ephesians 2:8-9).
Additionally, when Paul encourages the practice of the fruits of the spirit in Galatians 5; 19-23, we note several interesting things. The spiritual fruits are not works or actions per se, in the sense that we might normally think. There is no mention of our allegiance to the church, its doctrines, rituals, or most of its measures of piety. The fruits listed by Paul deal primarily with our state of mind, particularly our attitude toward our fellowmen.
In the same text Paul enumerates the fruits of the flesh. Even in that list, Paul's emphasis is more on state of mind than on specific behaviors. It makes sense that the fruits of the flesh would be the opposite to those of the spirit, meaning that those of the flesh promote sorrow rather than joy, strife instead of peace, arrogance in place of meekness, meanness rather than gentleness, and hate instead of love.
It is just too obvious that these spiritual fruits cannot exist within institutional Christianity with its obsession with resisting evil and demanding conformity. Little of the church's message and methods exude any measure of peace, love, kindness, joy, or humility. Theirs is a constant call to war against anybody outside their own tight doctrinal circle. War is not peaceful, loving, kind, joyful, or humble. Instead it is marked by the very fruits of the flesh which Paul condemns.
The many proponents of the "church at war" concept will have their favorite scriptures to support that; but, in practicing warfare, they do so by embracing the fruits of the flesh. War is not a spiritual practice, unless strife means peace, violence means gentleness, black means white. The state of war against all outsiders, to which the church is so committed, is devastating to any attempt to transform the human heart.
The ruthless warrior mentality of so many within institutional Christianity is not an expression of righteousness or nobility. Instead it is an insistence that Paul really promoted the fruits of the flesh rather than those of the spirit.