The threat to resign is just a rumor. So, I think it would be
premature to judge him based on that rumor. Comey appears to have a
good reputation for integrity and honesty. Here's an excerpt from
Wiki. Interestingly, here's a case where he has threatened to resign
before:
"NSA domestic wiretapping
In early January 2006, The New York Times, as part of its
investigation into domestic surveillance by the National Security
Agency, reported that Comey, who was Acting Attorney General during
the March 2004 hospitalization of John Ashcroft, refused to certify
the legality of central aspects of the NSA program. The
certification was required under White House procedures in order for
the program to continue.[16]
After Comey's refusal, the newspaper reported, Andrew H. Card Jr.,
White House Chief of Staff, and Alberto R. Gonzales, then White
House counsel and future Attorney General, made a visit to the
George Washington University Hospital to attempt to win approval
directly from Ashcroft for the program.[16] According to the 2007
memoir of Jack Goldsmith, who had been head of the Office of Legal
Counsel at the time, Comey went to the hospital to give Ashcroft
support in withstanding pressure from the White House.
Comey confirmed these events took place (but declined to confirm the
specific program) in testimony to the Senate Judiciary Committee on
16 May 2007.[17][18][19][20][21][22] FBI Director Robert S. Mueller
III, like Comey, also supported Ashcroft's decision; both men were
prepared to resign if the White House ignored the Department of
Justice's legal conclusions on the wiretapping issue. FBI director
Mueller's notes on the March 10, 2004, incident, which were released
to a House Judiciary committee, confirms that he "Saw [the] AG, John
Ashcroft in the room. AG is feeble, barely articulate, clearly
stressed."[23] Comey withdrew his threat to resign after meeting
directly with President Bush, who gave his support to making changes
in the surveillance program.[24]"
https://en.wikipedia.org/wiki/James_Comey