I'm still WAG'ing that there's some hope Ramirez still trusts Harry, has the POV that Harry is doing a deep-cover penetration of the Bad Guys to root out the White Council corruption & traitor(s). Carlos is just going through the motions, paying lip-service to the "
Harry Dresden is an incipient warlock... or worse!" party line amongst the more narrow-minded & reactionary (or just frightened) of the White Council.
I'm going back to
White Night, where (in the Raith Deeps) he says:
Oh come on, man... You're lying to me. You're lying to the Council... I'm not an idiot... You can barely get by in Latin, but you speak Ghoul? Ancient Etruscan? ... You're involved with these things. More than you should be. You know them too well. Which is a really fucking disturbing thing to realize, considering we're talking about a race of mind-benders... this whole thing feels more like a setup every second.
But then in the final chapter -- which is a series of "wrap-things-up" vignettes, of which Carlos' is the 4th -- they have their heart-to-heart, which includes:
Harry: "Gee. A Warden doesn't trust me. That's a switch."
Ramirez blinked at me. "What?"
Harry: "I had Morgan sticking his nose into every corner of my existence for my entire adult life."
Ramirez: "All hail the drama queen. Harry... I'm talking about you not trusting me, man."
Harry: "Uh. What?"
Ramirez: "...You think whoever is leaking information to the vampires is pretty high up, and the less anyone in the Council knows about what you're doing, the better... so you can't trust our own people, but "you're cutting deals with the vampires..." He narrowed his eyes. "You think you might be able to find the traitor coming in from the other side."
<snip a bit about Marcone's dealings>
Ramirez spread his hands weakly. "Was that so damned hard, Dresden? To talk to me?"
Harry: "No."
Ramirez snorted gently. "Idiot."
Harry: "So, think I should come clean to the Merlin?"
Ramirez: "Are you kidding? He hates your guts. He'd have you declared a traitor, locked up, and executed before you got through the first paragraph... But I'm with you, man. All the way."
So, we see here the deep-cover plot hatched between Harry & Carlos. Carlos
expects Harry to cut shady deals, to hang out with monsters, to alienate the White Council and get in tight with the Bad Guys(
tm). And Carlos is doing his part, acting like he's losing faith in Harry; even taking steps to "push Harry away" and further demonstrate his "reactionary
bona fides." In short, Carlos is acting like he's becoming a Morgan-esque hardcase. On his side, he's hoping that the "Bad Guys" will slip up, and he'll spot some clue(s) as to whose loyalties lay with the Black Council rather than the White.
And we see that Carlos knows Harry can be an idiot about these things. So, while Carlos can't be 100% certain Harry hasn't
actually gone Sith-mode, he has seen Harry go to the mat
repeatedly... always in favor of humans, and the underdog... and always against the Bad Guys(tm).
Moreover, I suspect Carlos gives a fair bit of weight to the opinions of the Knights of the Cross, who are
all friendly with Harry... and that speaks
immensely to which side of a fight Harry's going to be on (also, I suspect, it means the Bad Guys will never really be willing to trust Harry, and he's not going to get deep into any of their councils).