Really, this is all about Merlin because Merlin has a very big Harry problem.
Harry is individually very powerful -- a top 30 wizard in terms of raw Mega-Joules/Second. Harry is also very young, which makes that top 30 status concerning long term.
Harry is also Starborn (which is known to all of the Senior Council).
Harry is also extremely well-connected with Winter, Summer and the White Court. He also has unexplained ties to both Heaven and Hell, from Merlin's point of view. Heaven supports him -- based on his friendly relationship with the Knights; yet, Hell works with him too.
Harry also is The Warden, a position most recently held by ... Kemmler. Merlin understood -- though now everyone else does too -- that Harry possesses supernatural nuclear weapons. Ethniu and the Eye are the least of it, now.
If that were not enough, ...
Harry has supporters among the actual war-fighters -- the Younger Wardens. These are exemplified by Ramirez, Chandler, Yuki and Wild Bill (an actual subordinate of Harry). The commander of the Wardens, Lucio, owes possibly her very life to Harry due to the LaFortier incident (more on this).
Harry is also connected in the Senior Council as well, much more than a roughly 45 year old wizard should. He has unwavering support from McCoy and LtW. Conditional support from Rashid. Potential support from Liberty and possibly Christos as well. Meaning that depending on the issue, Harry has more support than Merlin (who can only rely on Mai). Note well, that the only Senior Council members not sent to the Battle of Chicago are Merlin and Mai. This is one reason that I think Harry might be wrong about Christos, though there are other reasons.
By the by, Harry was the BIGGEST winner in that whole LaFortier mess. LaFortier, Morgan and Peabody die -- none of whom are friends of Harry, really. Morgan and LaFortier were big supporters of Merlin. Luccio is saved and owes favors. Further, Christos may not actually be as anti-Harry (or even anti-Harry at all) despite appearances in Changes. Harry also appeared to be a Hero to much of the assembled council (that survived).
Then Harry completely ends the War with the Reds, seemingly dying in the immediate aftermath, only to rise again to confront the Fomor.
So, if you are Merlin, Harry absolutely f-ing terrifies you to your core. What, therefore, is your reasonable first step? In true British Empire fashion, you secure your power base and divide your enemies. You can't influence Mab or the White Court or Heaven and Hell. However, you can drive Harry apart from the supporters he has among your own people.
You can make Ramirez and the Younger Wardens suspicious of Harry. You can arrange things to get the Senior Council members that support Harry see how in thrall he is to Mab or the White Court or both. The fact that McCoy, LtW and Christos -- the most combat focused of the Senior Council got injured and weren't able to vote for Harry was a nice bonus.
Of course, Merlin also set things up a later win-win with McCoy. Either McCoy goes rogue and refuses to take out Harry and Merlin wins by getting rid of McCoy. OR, McCoy take out Harry and Merlin wins by removing such an unpredictable and dangerous person.