I am by no means considered a veteran rider, but would like to comment on the original poster's story and my thoughts...
When riding in a group, you are responsible for determining safe distance both in front of AND behind. Now, I'm not saying that the rider behind you was not at fault or was..but from what you are saying, it seems that by your own words you were not experienced enough to conform to this rule of basic safety and therefor should not have been riding that day in the group. I can't help but get the impression that the group you were riding with were all riding close together and you stopped abruptly without checking your rear, in which case the rear driver may not have even had a chance to stop in time.
You mention that their injuries were severe and had to be air lifted out. Yet, you stated that you wanted everyone to continue on...because you "spent a lot of money and time to be there" (paraphrasing). I would have found that extremely disrespectful if I were there, especially since you were part of the cause. I could understand and agree that you should not be called back to participate and to be honest I don't know what kind of guys they were but if someone acted like that when it was my brother or relative laying on the side of the road..we wouldn't have been so nice to someone acting so callous.
That fact that an officer who was not there says you were not at fault holds no weight with me. The fact that you state that riders who were there hold you at fault does.
I think you posted this thread not to find out whether you were in the right or wrong, but to make yourself feel like you are not wrong and what they did by banning you was wrong, and I'm sorry but I don't agree.
I really think that you are genuinely sorry for what occurred and have no doubt that it's stuck in your mind. How could it not? But I'm sorry it's just that I don't agree with the majority here.