Someone probably already pointed this out, but I really don't think that Dean meant his Please Don't judgemental way. I suppose he meant "Please don't tell me now of all times, now that I'll lose you". I think that in this moment, there was nothing but rage in his mind that Cas would be so cruel to hurt him like that, to put the pleasure he'd get out of finally confessing over consideration for the pain Dean would have to endure by living on with that information after Cas has died.
This isnât Dean saying âDonât tell me that you love meâ. This is Dean saying âDonât tell me that you love me right before youâre going to dieâ
And look at Cas after Dean tells him that
This is Cas saying that he loves him and thatâs why he is doing this; to save Dean.
And look at how heartbroken Dean is knowing that Cas is about to die
You donât make those faces because you donât want your best friend telling you that he loves you. You make those faces because your best friend loves you and he is telling you that seconds before dying just to save you.
And you donât make those faces if you donât feel the same way.
Dean has always hate it when Cas leaves. Dean was so pissed about it in 15x09 that he said it:
And now, Cas just confessed his love for Dean and he is about to die. And Dean doesnât want him to die, he doesnât want him to leave him. Look at Dean, saying Casâ name right before Cas dies
He says so softly, still not processing whatâs going to happen. He is still in denial, he doesnât want Cas to die. So he looks at him, pleading, because he canât let him go.
A lot of people are complaining about how Jensen played this scene, because Dean is barely emotional, at least vocally. But you can see in Deanâs expressions how much it is hurting.
Overall, Dean is shocked. In a matter of minutes, Cas told him about the deal, then he told him so many beautiful things, things that Dean refuses to believe, because he hates himself so much that every time someone praises him, he doesnât believe it, because he feels like he is the biggest piece of shit in the world. And when someone tells him that that isnât the case, Dean doesnât know how to respond or react, because he canât accept those words.
And after all that praising from Cas, Cas tells him that he loves him, and Dean who considers himself not worthy of love, is so shocked and so overwhelmed but at the same time, he is conscious about how happy Cas is and that it means that Cas is going to die.
Dean has to process all of that in just a matter of minutes. 12 years of their relationship is processed in just a few minutes. There is so much love directed towards Dean in just a few minutes, more love than he has ever had in his whole life. So Dean reacts like this.
He doesnât say âDonât do this, Casâ because he doesnât want Cas to tell him that he loves him. He says it because he doesnât want Cas to die right before he tells him that he loves him. Becuase if Casâ death at the end of season 12 almost destroyed Dean, this one is going to destroy him completely.
