If there is fear in you, and if you are projecting it outward, you will project it onto specific things. This is because fear is divisive and not whole, so it attaches to PARTS OF the environment. And in particular it can project onto a specific body.
When fear is projected, another's body is seen in a very isolating way. Fear distorts perception heavily and anchors you into the physical. It then seems that only the physical exists, only the physical rules apply, only physical causation is real, and there is no escape from anything.
By making your brother's body his "reality", focusing on its condition or form or appearance, projecting fear onto it, you turn it into an enemy. You give it power over you. Your whole awareness sinks into the ego and you can find no way out.
As the body is given reality, which is very easy to do when you are afraid, your whole focus shuts out the mind and awareness of any higher truth. And now you feel like you are completely imprisoned and held captive by this "sinful body" you see. Like you are locked in and completely at its effect. Anything it does, or doesn't do, now seems to completely affect you against your will, as if you have no ability to stop it or do anything about it. If the person has a sickness or problem and cannot fix it, or isn't trying to, you will now feel like they are imposing limits on you and forcing you to suffer.
Seeing yourself as a victim of this dynamic, already deep in fear with nowhere to turn, everything now seems like a closed system. Having bound your brother to his body, imprisoning him, you see yourself as imprisoned. And now your brother's body seems to be attacking you. This incites reactions of even more fear, which turns into anger and rage, justified due to what he seems to be doing to you.
It will now feel like there is nothing you can do to be free, as if your mind is somehow locked onto their body state, as if you have merged with it and are kind of one with their body. You will feel exposed to it and completely vulnerable to it, as if you have opened up a conduit or bridge, a cord that has bound you to it. Its every move seems to dictate your suffering, and you cannot seem to be free unless the other person changes. And now you will demand they change, rather than look at the fact you are projecting fear.
This really is the ego's version of "forgiveness to destroy" taken to the extreme. The projection of fear blinds you to stepping back or looking into your mind, seeing yourself as doing anything to yourself. It warps your perception and turns it inside out. Cause and effect are backwards and you see yourself as completely victimized. The more you go into it the more you lose sight of the fact that you have any power or are choosing any of this.
Your whole sense of peace then seems to completely "depend" on the other person. If their body has any issue at all, you'll blow it out of proportion and see it as a threat and a danger. And how dare they not resolve it for your benefit. The only way out of this is to stop projecting fear, look at the fear within you, heal it and return to love.
True forgiveness is needed, and you must be clear that fear really is an attempt to attack. "The fearful are apt to be vicious." Viciousness comes out when you are afraid. And by attacking, you will see another as attacking you. And having attacked them by seeing them as only a body, you will see their body as attacking you. Just even by sitting there in its condition, it is experienced as a threat, because you have threatened it, having threatened yourself.
Fear is really part of your self-attack, resulting from guilt, resulting from a belief in sin. Your own sinlessness is the key to salvation and to removing the basis for fear. There is nothing to fear because only love is real.
"It seems to be the body we feel limits our freedom, makes us suffer and at last puts out our life. Yet bodies are but symbols of a concrete form of fear."
"But fear attaches to specifics, being false."
"Bodies attack, but minds do not." "This is the reason bodies easily become fear's symbols."
"The body is the target for attack, for no one thinks he hates a mind."
"When hatred rests upon a thing, it calls for death as surely as God's Voice proclaims there is no death. Fear is insatiable, consuming everything its eyes behold; seeing itself in everything; compelled to turn upon itself and to destroy."
"Who sees a brother as a body sees him as fear's symbol. And he will attack because what he beholds is his own fear external to himself, poised to attack, and howling to unite with him again. Mistake not the intensity of rage projected fear must spawn. It shrieks in wrath, and claws the air in frantic hope it can reach to its maker and devour him."