That's a surprisingly dismissive reading. The first external source cited is Abramson. Every other source cited in the letter was also cited by Abramson in his original thread [1].

The letter summarizes Abramson's allegations: "The facts point to a coordinated effort by some in the FBI to change the course of the Clinton investigation by leaking sensitive information to the public, and by threatening to leak additional information after the investigation was closed."

There are no two ways about it: Either Abramson is onto a huge story that hasn't been reported elsewhere -or- sitting members of congress take investigative actions based on the ramblings of an irresponsible conspiracy theorist. Both are concerning.

[1] https://threadreaderapp.com/thread/939432544008921088.html