Deputy Attorney General Rod Rosenstein obstructing Congress' role of oversight

Deputy Attorney General Rod Rosenstein keeps on obstructing Congress' role of oversight.  Rosenstein is preventing Congress from interviewing the FBI agents who interviewed General Michael Flynn and said that he didn't lie to them.  Special Counsel Robert Mueller ignored the evaluation of these agents, the ones who were actually present when Flynn was interviewed, and charged Flynn with making false statements.  It is understandable that Congress would want to talk to these agents, though it is understandable that Mueller might object to this oversight.

But Republicans on Capitol Hill are seeking more information about that interview as recent revelations have raised questions about the guilty plea itself. They say former FBI Director James Comey in fact indicated to lawmakers that FBI agents did not believe Flynn intentionally lied about the talks with Russia’s ambassador. 

“Contrary to his public statements during his current book tour denying any memory of those comments, then-Director Comey led us to believe during that briefing that the agents who interviewed Flynn did not believe he intentionally lied about his conversation with the Ambassador and that the Justice Department was unlikely to prosecute him for false statements made in that interview,” Grassley wrote in May to Rosenstein and FBI Director Christopher Wray. . . .

Now in an escalation of the tensions between Congress and Rosenstein, we find that Rosenstein threatened to subpoena Congress' emails, phone records and other documents from lawmakers.  Does Rosenstein realize that oversight is Congress' job?  Rosenstein has been upset that Congress is keeping a record of their interactions with his office, but why is that wrong? 

“The DAG [Deputy Attorney General Rosenstein] criticized the Committee for sending our requests in writing and was further critical of the Committee’s request to have DOJ/FBI do the same when responding,” the committee's then-senior counsel for counterterrorism Kash Patel wrote to the House Office of General Counsel. “Going so far as to say that if the Committee likes being litigators, then ‘we [DOJ] too [are] litigators, and we will subpoena your records and your emails,’ referring to HPSCI [House Permanent Select Committee on Intelligence] and Congress overall.”   

A second House committee staffer at the meeting backed up Patel’s account, writing: “Let me just add that watching the Deputy Attorney General launch a sustained personal attack against a congressional staffer in retaliation for vigorous oversight was astonishing and disheartening. ... Also, having the nation’s #1 (for these matters) law enforcement officer threaten to 'subpoena your calls and emails' was downright chilling.” 

The committee staffer noted that Rosenstein’s comment could be interpreted as meaning the department would “vigorously defend a contempt action" -- which might be expected. But the staffer continued, "I also read it as a not-so-veiled threat to unleash the full prosecutorial power of the state against us.” . . .

Is this proper behavior for a member of DOJ to treat Congressional staff who are overseeing his activities as criminals? I suspect that this type of threat is incredibly rare.