In such a case, those who launch the DDoS may have no legal/legitimate grounds to take some disfavored content down. (Perhaps it is embarassing to their prophet, government, guru, criminal enterprise, or movement.) They may have asked for material to be taken down, and the hoster said, "no, it's legal content" – at which point the DDoS is launched as both primary censorship (disabling access to the whole site) and censorship-by-blackmail ("take it down or your whole site stays down").
On the other hand, it's also possible that the originators of the DDoS are angry about something the hoster did take down. Perhaps they'd put up material against the rules, Pastie took it down, and in a tantrum after-the-fact, they decided to retaliate with a "well if you won't host our stuff we'll block eveyone". (This is a bit more like the Anonymous DDoS against payment services they didn't like.)
Without a statement from those involved, it can be hard to determine DDoSer motivations, but those are some common patterns.
On the other hand, it's also possible that the originators of the DDoS are angry about something the hoster did take down. Perhaps they'd put up material against the rules, Pastie took it down, and in a tantrum after-the-fact, they decided to retaliate with a "well if you won't host our stuff we'll block eveyone". (This is a bit more like the Anonymous DDoS against payment services they didn't like.)
Without a statement from those involved, it can be hard to determine DDoSer motivations, but those are some common patterns.