Blind Desire:

[vagabond]

"Although gold dust is precious, when it gets in your eyes, it obstructs your vision." ~Hsi-Tang

Blind Desire

The strength of a man is to found in his heart,                 " a man´s strenghth lives in his heart"
and not in his arms or legs,          < ---  I would leave that line out.
to that which his will clings he'll never depart        "from what he clings to he will never part"
no matter how much reason begs!             i am not sure if reason always begs against a strong will. i think it shouldnt.
He will live for a belief, he'll die for a cause,
this iron will's his greatest virtue,
he'll wrestle with demons vile without pause
for that which his heart holds as true
And sacrifice all that he has on a whim
in fiery feats of integrity;                                       by your poem´s first line you attribute all this senseless fighting mode to every man. this seems improbable.  You could begin the poem with an anonymous "His strength ..." so that you describe only a certain type of person, which doesnt even have to be male (except for the rape part)

but truth is a phantom, ghastly and grim,
when his reasons are in-sanity;                                   here I would want you to go deeper into the special nature of this insanity.. it is so vague a word.. but I admit that I can´t offer a good choice of words myself.
See brothers fight brothers for forests and fields,
treasuring but greed and pride,                     you wouldn´t really treasure greed and pride
And women are raped "for the pleasures it yields",                 this feels like a pretty abrupt change of topic as rape has nothing to do with a strong will 
for shame my soul flees to hide.
Yea the faults of all men are to be found in their hearts
alongside their greatest virtue,
for when passion is roused, reason departs           not always a bad thing if reason departs. you could write conscience instead of reason.         
and men heed not what they do...