He knows what he's doing.

i am run through and through with disaster; i am knifed to the hilt with fate.

Oh, hell no. Panthro is mine.

He JUST grieved Cas. He JUST got Cas back! And now he's finding out Cas was held captive for WEEKS without him knowing. The guilt is obvious. He's showing Cas how bad he feels and how sorry he is. But still, Cas has no idea what Dean really means when he says he's sorry.

Cas thinks Dean's sorry is pointless. "Well, [Asmodeus is] a shape-shifter. Besides, I-I was the one who got myself captured."

But Dean's really saying, "I should have known it wasn't you because I know you. I failed you, and I hate myself for it. I just got you back, and I already let you down."

While Cas is focused on, "All I care about is finding Jack and your mother and fulfilling my promise to Kelly and getting you back your family."

And that's how what Ackles said post finale makes sense. Dean didn't think Cas was capable of [romantic] love. A human would understand what Dean is trying to say here, but Cas isn't human. How he feels doesn't matter. It never has and it never will. Only it's always mattered to Dean, Cas just couldn't see it.

So, like, you have Dean standing here (groveling), apologizing to Cas for failing him.

And you have Cas standing here saying it's all his own fault for not being good enough.

these sam lines from 1.11 Scarecrow have always struck me as such a cruel thing to say (and i know dean forgave him immediately because he’s a sweetheart but i was put on this earth to hold dean’s grudges for him and holding this one i am) even though i get they were coming from a place of heightened emotion. it’s just, only two episodes since 1.09, when dean admits to sam for the first time ever that mary’s death haunts him so badly he swore to himself he’d never go back to lawrence again… just feels disproportionately mean.

but on this rewatch it’s the lines before it that hit me:

sam is an obvious john mirror starting as early as 1.01. it’s not particularly subtle, and the show definitely wants you to pick up on it. it’s not just the similarities in their storylines, ie. losing their partners to the same entity; it’s in their natures. their tendencies toward fanaticism, toward obsession. the driving force behind what keeps both of them hunting in s1 is revenge.

the common fanon misconception is that s1 dean is the one who wants to find john the most, that he has an unchallenged and uncritical devotion to his father, that he hunts because he’s trying to emulate john, that he’d do anything john tells him to. and yes, he’s on this hunt in 1.11 because john contacted them for the first time in months and ordered them work this job. but what we’ve been shown for most of the season is dean leading sam on hunts under the weight of john’s total radio silence, helping people because it’s the right thing to do, and not really looking especially hard for john at all after 1.02. in fact, in that very episode, sam wants to abandon the hunt (and the people they’ve started helping) when the trail to john goes cold, and it’s dean who has to convince him to stay and rescue everyone.