If they actively ignored death threats/didn't send them off to the police when it came to their attention, they become responsible.
"The costs of bad actors are your costs."
Cloudflare is sick and tired of getting attacked by people from the TOR network. I don't blame them for the ban. It's costing them money..and TOR isn't going to raise the funds to pay them for the lost bandwidth and customer revenue.
We used to have a bigger problem with mail spam because server operators constantly would leave anonymous relaying open. How did we stop a great deal of it? By blacklisting the IP until the problem is fixed. It has worked out pretty well.
"And you should realize that in doing it you're knowingly hurting innocent people."
I guess we have to determine which 'innocent' people are more important: The ones getting their websites attacked and hacked anonymously, the people that can't access those websites because they are down/DOS attacked, or the random people that want to use the TOR network.