Barr is a political hack at this point. I am disappointed in having to say that because I had high hopes for him showing some integrity. But it is not to be.
You start with his affirmative statement that Mueller's investigation showed that there was "no collusion." That, to me, is similar to instances in which people see results of a statistical test failing to show at high confidence that there was an effect saying that it showed "no effect." No. That's not how it works.
Here is a quote from the Mueller report:
Second, while the investigation identified numerous links between individuals with ties to the Russian government and individuals associated with the Trump Campaign, the evidence was not sufficient to support criminal charges. Among other things, the evidence was not sufficient to charge any Campaign official as an unregistered agent of the Russian government or other Russian principal. And our evidence about the June 9 2016 meeting and WikiLeaks' s releases of hacked materials was not sufficient to charge a criminal campaign finance violation. Further, the evidence was not sufficient to charge that any member of the Trump Campaign conspired with representatives of the Russian government to interfere in the 2016 election.
That is not, "We showed that there was no collusion." And Barr using that "collusion" terminology is particularly bad in view of the fact that Mueller went out of his way to move away from that terminology. As in:
As an initial matter, this Office evaluated potentially criminal conduct that involved the collective action of multiple individuals not under the rubric of "collusion," but through the lens of conspiracy law.
There's just no way to defend what Barr did. He did not present an honest assessment. He's clearly identified himself as a political hack.