I have little desire to conquer the Imperium, I want to break it, shatter it into thousands of technobarbarian kingdoms to struggle and compete amongst themselves, letting the game unfold on a million battlefields across the stars.

In any case, we do not need to face the Imperium in a conventional fight, that is not where our strenght lies, at least not in comparison to the raw power of industry that the Imperium has. No, we must awash the galaxy with the song of chaos, let every man woman and child here the whispers of the warp, its promises of power and prestige, and set the slaves upon their masters. The countless Warbands can descend upon the ashes as saviors, exterminators, or conquerors as they see fit, carving up the galaxyinto competitive kingdoms. The Imperium cannot strike everywhere at once, and the spread of chaos can go everywhere, they will be scattered and weakening, their empire fighting itself, and we would need only minimal forces per system. Only enough to ensure the song is heard on every world.

That was well put, but lets face it, CSMs won't think they've 'won' until they have the Emperor's skull for a chamber pot. Of course once that happens warp travel (for the imperium) dies without the astronomicon.
Then its buffet time for the Tyrannids! catch-22

Ofcourse they would, but with out the Imperium buffeting off the Tyranids (somewhat) the rest of the galaxy is on the menu. Maybe they woun't be able to enter the eye of terror but even so if the Emperor was cactus (and didn't reincarnate/super saian whatever) they will come a day when CSMs will look out on the galaxy and see a lot of dead rock.

I'm not really going anywhere with this point other then to say that if CSMs were to succeed in their ultimate goal they would also lose and the chaos gods with them as there would be no more imperium to feed on.
Tis a bit morbid but fits the w40k style

Since so many people disagree with me on the whole "Imperium of Chaos" idea, what is our actual goal? Seriously, what are we fighting for at this point? I was fighting for a future where the Word of Lorgar is heard and spoken by all of humanity.

I fight for decay. A khorn marine fights for blood and glory. One of Tzeentch's marines fights for knowledge. Slaaneshi Marines fight for the sensation of it. Mostly, chaos fights for the sole purpose of fighting.

One could even say, we fight for Chaos

The fact that any of you presume to understand and interpret the will of the Dark Gods is absurd if not somewhat amusing. No mortal could ever hope to understand machinations enforced by Gods that feed on our hopes and fears. All beings are puppets, actors in the greatest of plays, willing or unaware of the roles they play but participants none the less.

Those of us that serve the ruinous powers aren't "enlightened" we aren't prophets of the end times but simply lost souls that were too weak to resist them. We gave into our fears, our ambitions and desires long ago where as the "righteous" blinded by faith or too ignorant to know any better press on, unaware of the inevitability of it all. All things bow down to Chaos one way or another, in some shape or form at some point in time.

Why must there be more to it then that ? Isn't Chaos enough ? Are all the pain and suffering, loss and destruction, corruption and ruin, despair and hopelessness not enough sustenance to maintain the grasp the Gods hold over all things ? I hold no illusion over what I have become, I serve if only to bring these things full circle, nothing more, we are terrorists in the greatest possible sense of the word.

This is no quest for domination, there is no game plan at least on any level we could ever possibly hope to comprehend, these events have been unfolding since long before our time and will continue well after we are nothing more then tormented souls, long lost and forgotten.

Fight to break the False Doctorine, end the tyranny of the Emperor, and to revel in the glory of chaos. Competition brings evolution, so to shatter the Imperium is to bring humanity forward. Why simply replace one tyranny with another?

If that is the true nature of the faith I was born into, then I need to do some serious soul-searching. If you need me, I'll be in the Warp, begging the gods to give me some kind of solace or understanding of my life. I (as a 40k character) have never felt so lost. I don't know how to serve my gods. I have my faith, but I don't know how best to bear that faith.

Because we need to be unified, or else the Xenos (especially the Tyranids) will destroy humanity. The truth can wait. Survival is more important. We can't serve the Gods if we are extinct.