McCabe directed underlings to confirm an FBI investigation into the Clinton Foundation shortly before the election. That was a violation of FBI policy -- you don't confirm or deny the existence of investigations while they are ongoing, particularly when they are political in nature. McCabe then got into trouble when he lied about it, denying that he had authorized the disclosure and claiming he didn't know who made the disclosure.
So I don't think it's a right/left issue -- I think he violated FBI policy, then lied about it.