Where did you learn that the DNC sis not cooperate with the FBI? One of your favorite youtube channels?
This is from Politifacts:
http://www.politifact.com/truth-o-meter/statements/2017/jul/11/donald-trump/did-john-podesta-deny-cia-and-fbi-access-dnc-serve/
First, the American intelligence community (FBI, CIA, NSA and DNI) stated: ""The recent disclosures of alleged hacked e-mails on sites like DCLeaks.com and WikiLeaks and by the Guccifer 2.0 online persona are consistent with the methods and motivations of Russian-directed efforts,"
Further:
"n his testimony in January on the cyber attacks, then-director of the FBI James Comey said the agency never got access to the machines themselves, but obtained access to the forensics from a review of the system performed by CrowdStrike, a third-party cybersecurity firm."
That may be the basis for your idea that the DNC did not cooperate.
But
"We got the forensics from the pros that they hired which – again, best practice is always to get access to the machines themselves, but this my folks tell me was an appropriate substitute," Comey said.
In addition:
"The DNC coordinated with the FBI and federal intelligence agencies and provided everything they requested, including copies of DNC servers," Watson said. She added that the copy contains the same information as the physical server.
The FBI joined CrowdStrike’s efforts to boot Russia from the server, but then-Homeland Security Department secretary Jeh Johnson complained the DNC rebuffed their offer to help. This was because Russia was already out of their system by then.
If you are referring to an earlier period in the summer of 2015, it has been reported that the FBI was calling an IT desk help phone line manned by a contractor, who did his own search and found nothing and left it there, without kicking it up the chain of command, not did the FBI contact any of the executive leadership of the DNC at that time
I can understand denial of collusion, which is complicated, but to deny that we have proof that Russia hacked the DNC is like denying climate change. Even Trump's intelligence leaders admit it freely.
While you might be able to make an argument that DNC could have done more before the fact, both with protecting their servers and paying more attention to the low-level FBI warnings, they certainly cooperated sufficiently after the fact to determine who had carried out the cyberattacks.
Even in a world of hypotheticals, if the DNC was partially responsible for not preventing the attacks, would that give the Trump campaign the right to weaponize the information by coordinating with the hackers in terms of content and timing of the release? If the hacker were domestic, it would they would be considered to be part of a conspiravy.