Regardless of whether it is free speech or not, things that are detrimental to their primary business or impact other clients, violate their T&C. I would have turfed them too.
The attack is politically motivated. You don't see anyone attacking tpb because they maintain a tracker link to the 1.3tb archive. The attack is specifically against the domain, causing wikileaks to jump around from provider to provider. The attack doesn't prevent the data from being distributed. Four newspapers already had complete copies - one of which hired 12-14 people to write an interface in Django to collate and categorize.
The DDOS does nothing but prevent the people that want to casually see what the fuss is about from seeing it.
If you're that concerned that the information should be free, grab the 1.3tb copy and host it. Yeah, that's what I thought.