I like how far Drift came in terms of his opinion of the Circle Of Light. I can’t speak of the time the Circle were involved in MTMTE (I haven’t read that yet), but Drift willingly being referred to as a Knight later and being subordinate with Dai Atlas really shows his change.
His time with Wing, spending time talking to him, training with him, changed him in ways he probably doesn’t want to admit, at least during the time of the change. He definitely got mellowed out and slowly started to learn that the Circle weren’t cowards, were so much more than Drift originally thought, which is one of the reasons why he ultimately chose to tell Dai Atlas of his deal with the Decepticons.
Spending time with Wing allowed his opinion of the Circle be changed positively. Wing probably took him sight-seeing around the City, allowing him to see the inter workings of it, maybe even learning of its history, which helped changed his opinion. I think Wing also being able to beat him in a fight bruised his ego, but also made him respect Wing and the other Knights in a way. After all, would cowards learn to fight so well? Drift himself, or rather Deadlock, was already a skilled warrior in the Decepticons, and here a whole part of a society could beat him? It was impressive but probably also a huge shock.
The fact that the Knights, that Wing, were willing to sacrifice their lives for the sake of the City supported his growing opinion that they were weren’t cowardly for leaving, in fact they were incredibly brave. The fact of the city being raised and all of its civilians (non-combatants mind you) were ready to give their lives implemented his opinion even more.
He gave the Circle a hard time about them leaving for the war, but I think deep down he knew that many of the Decepticons and Autobots were cowardly in their own way. I mean, most of the Decepticons joined because of their own sadistic reasons, and many of the Autobots were previous senate members, both of which I imagine wouldn’t give their life for their cause. The fact that these scientists and civilians were willing to do what his own warriors wouldn’t? Willing to give their life because of a strangers, a previous enemy’s, mistake? It was a truth he couldn’t fully face yet.