There was some copypasta about this, actually. Kharn invited them into the beserker fold. The Angry Marines almost considered it, but then one of their Angry Chaplains called Kharn a pussy for daring to think he could be as pissed off as the Angry Marines. The Angry Marines then proceeded to beat some heretic face in.

The aspiring Champion of Khorne called out to the Angry Marines before him just as they prepared to charge his host of daemons and World Eaters. "Can you not see the similarities between your battle prowess and ours? Khorne fills you with his wrath in battle, but you do not take time even to notice. Join us, and together we can destroy all within our path! Sink deeper into your anger with the full blessings of the Blood God!"
The assembled Angry Marines took pause, and considered the words of the World Eater Champion. It wasn't until Chaplain Brusiarch stepped from the front ranks of the Angry Marines' line, turned, and backhanded the closest Angry Marine that the yellow-clad battle-brothers turned their gaze towards him. Brusiarch turned towards the aspiring Champion and pointed to the bolt pistol in his left hand. The Chaplain then shouted to his brother Marines, "YOU DON'T LISTEN TO [see forum posting rules], YOU COCKSICKLES, YOU fething KILL THEM!!!"
The previously backhanded Space Marine then stood up, his faceplate shattered from the force of the blow, and shouted the battle cry of the Angry Marines, "ALWAYS ANGRY!!! ALL THE TIME!!!" The Angry Marines then realized their folly at listening to a [see forum posting rules] who dared consider himself as angry as they, yet arm himself not with a second chainsword or power fist, but a pussified bolt pistol. The next few seconds witnessed the roar of the Cocknocker's jump packs, the whoosh of battle-brothers being launched at the daemonic host from the Predator Angrinator's, and Brother Chaplain Brusiarch's battle cry of "FUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU-," as he charged the World Eaters' line.

From the personal diaries of Brother R.C. Mongler, 4th Chanian Combat Group.
+++++
My Chapter had landed on a barren little ball of rock called Vesuvius. The Inquisition had ordered us to the planet on suspicion of Chaos corruption. Surely enough, we ran into a group of Chaos Marines within a day of landing. The fools, turning their backs on the God-Emperor for whatever sick rewards they received from the deceiving Warp fiends. The battle started the second morning. Their attack was especially fierce, and my brothers and I had great trouble keeping them at bay. It seemed that for every one of them we killed, three more showed up. Our own losses were of no small concern. In a rare moment of calm, Brother Captain Morgan confided in me that if we were not killed by these berserkers, we would almost certainly be killed by the Inquisition for failure. As our numbers dwindled, I grew concerned: surely we would all be killed, and the Emperor's work would not be carried out. We prepared for a final assault, one which had been coming for near a week of the most intense fighting I had ever seen. We surrounded a small hill, atop which stood our last Dreadnought, Brother Klarr. We saw their force coming from below. We knew this was our end. But suddenly, a shadow passed over us. Some great demon come to finish us off? No. It was a drop pod. Out of it stepped a small company of our brethren. They wore bright yellow armor, a bizarre crest upon their shoulders, unlike any Chapter I had yet heard of. A circle, with two lines crossing it and two dots in the middle - almost as if to suggest an angry face. They formed a line between us and the now charging Chaos Marines.

The Chaos Marines' bright red armor shone in the late afternoon sun, the spikes upon their shoulders menacing. The new arrivals stood fast. As the distance between the two forces began to close, there arose from these yellow warriors the loudest scream I had ever heard. It shook the ground. Even through my helmet, it made my ears ring and my skull ache. And it simply kept getting louder as their Captain's fist slowly rose into the air. As it rose to a nearly supersonic volume, I finally made out the words contained in the scream:

"ALWAYS ANGRY!!!"

In a chorus louder even than the Captain's scream, the soldiers returned:

"ALL THE TIME!!!"

Then it began.

...

Without a word, these Space Marines returned to their drop pod and were soon whisked away from the battlefield. There had been no more than a dozen of them, not a single word exchanged between our two Chapters. To this day, I have never seen any Marines fight with such rage and hatred. The mass of enemy berserkers was reduced to mere chunks, legs, arms, heads, and craters full of blood. Bits of red armor lay strew about the field. We had not even had the chance to advance by the time the screaming - both theirs and the enemy's - was through. I turned to my Captain and asked, "Who were they?"

"I had thought it was rumor, but no. Emperor bless us all, those were the Angry Marines."