My two cents with respect to this unfortunate aftermath. My initial reaction to Castiel's monologue was that it was some understanding on his part that, although he can never be human, he experienced what he could through his association with Dean and others. I thought the "I love you" was the ultimate feeling that humanity experiences. Dean's reaction was that of shock because his friend told him he would soon be dying, having made a deal, while Death is pounding on the door. There's a lot going on and much to process. How anyone could have interpreted Dean's silence as anything other than stunned is beyond me. I did get the brief impression of repulsion. This is not a reaction to a potential '"gay confession" but rather the way many react to sudden bad news. However, as a viewer, I found that monologue to be one of the most poorly written and badly acted scenes I have ever witnessed. This may also account for that hint of incredulity that crossed Jensen's face while Misha was hamming it up.
I liked Castiel up until season 12. His focus on Jack, repetitive sappy dialogue, eye rolling and pursed lips were a chore to watch. Though, now, I have encountered Misha Collins. It is impossible not to. I have come to understand he gives his phone number out to depressed little girls and boys, capitalizes on selling his merchandise to them and serves as a beacon in the night to all their woes. He took it upon himself to interpret the monologue the way his fanatics would wish it to be without consideration for: his costar's interpretation of an 11 year old brotherly bond, the interpretation of the majority of less vocal viewers, or the ramifications of insults and injury to Jensen, the show and the viewers. His pale attempt to put out the fire he started and the flames he fanned is laughable and self-serving. He wasn't the hero of the story, and he is not the hero in this controversy. He's an instigator, an opportunist, a whore.