In real life, we can't expect "a custom fit in an off-the-rack world," as Hawkeye Pierce told Margaret in a 1979 episode of M*A*S*H. What this means is that, when we get close to someone--anyone--then there are going to be points of conflict and contention.
Bach's book launches from this Fact of Life: that arguments are inevitable in relationships (pp. 17-33), so what we must do is take care to ensure that these arguments don't become toxic and poison intimacy. Rather than trying to avoid all conflict (which has toxic effects, as well), Bach's book sketches a middle ground: If We Have to Fight, Let Us Learn to Fight Fairly! In fact, in what might seem to be a paradox, arguments--"fair fighting"--can actually be bridges to intimacy, since they provide a stage for couples to canvass, compare and contrast their deepest desires and most personal aspirations. Toward that end, Bach offers specific guidance on "How to Fight a Fair Fight."
By way of background, a couple of notes are in order: (1) Bach's understanding of aggression's psychology owes a lot to Konrad Lorenz's 1966 book "On Aggression." (2) Bach shares Eric Berne's view (in his "Games People Play" (1964)) that some people avoid the vulnerability of intimacy through playing "games"--i.e., playing (masked) roles in patterned rituals which are comfortably predictable, but at the price of robbing their "players" of real self-revelation and mutual intimacy. (One famous dramatic example of this, which is never far from Bach's thoughts, is Edward Albee's drama, "Who's Afraid of Virginia Woolf?" (1962).) Readers of Bach's book might find a pre-reading of these three sources helpful to appreciating Bach's diagnosis of intimacy-failures in relationships, and the "fair fighting" prescription he offers for remedying the problem.