What stood out for me was the idea that the offending person(s) can use botnets to bring down networks. If you think about it, they've essentially invaded the host systems like a virus, and use them to overwhelm a network. So how do you ultimately defend against that? I don't know enough about this to make a judgement on that, but it seems to me that it would be difficult.
I hope the person(s) doing the DDOSing will just move on. It's a pointless fight at this stage. You've made your point. Stop being a bully. Admins on this server have to make choices. Some of those won't be good choices. But somebody has to make them. You can't expect admins to be perfect and understand things without error. If no one made choices, especially the kind that are final, then nothing would get done. Get over it!
If the attacks keep going on, I hope something can be done about it, but it doesn't look good to me. If this person or persons wants to cripple the network, I don't think it can be stopped. I don't know that, but I suspect that much. The previous hosts said they could stop it and it was not true. So...
And for fun, for those who haven't seen it, my favorite remix:
http://www.youtube.com/watch?v=JImcvtJzIK8