Good review, I should have read it and skip the episode because I almost fell asleep.
Like you said, problem with Mac is that he is too often this two-dimensional guy that only sees good and bad. I had some hope after S5 where he was beginning to act more sympathetic towards those whose morals didn't agree with his, but this episode was definitely a step back.
What's the point of digging into Mac's past if we are only going to see how faultless his morals and believes have always been?
Mac didn't always made the wisest choices both in his past --as seen in the 333 arc-- and at present --Clay Dobson's death--, but at the end Mac remains the same. He never learns a thing and he's still right all the time. Righteous!Mac man frustrates me immensely.
While I was watching "Blacklist" I kept thinking of Miami's last episode, "Hostile Takeover" and their similarities. Both "bad" guys felt that justice wasn't done and felt betrayed by the system. Both asked for the CSI leader to listen to their plight and help them. But Horatio, even when he's Super H, is far more sympathetic than Mac, so the episode fell flat in comparison.
Gravedigger definitely should have been chosen another character.