ok and i love that cas kinda skirted around the nature of bejamim and his human paramour’s relationship. Much like with all things “relationship,” all things “danger,” all things “intimacy and sex,” it triggers a strange awkwardness in Cas and Dean in later seasons (because they want each other; it’s the elephant in the room).
I don’t have the GIFs, but Cas seems almost relieved when Sam swoops in to provide neutral wording, which allows Cas to breeze past having to talk about angel-human relations.
Clearly, it’s something that makes Cas uncomfortable both because of his upbringing and the forbidden nature of his and Dean’s feelings. We learn that it’s not just any law, it’s the oldest law in Heaven.
And soldier angels are rife with misanthropy from what little we’ve seen. If misanthropy is that saturated in the military wing (see: Uriel) then it’s no wonder Lucifer found such easy support, (or that AU Michael was able to switch to genociding humans after defeating Lucifer).
CAS: Benjamin is an angel. His vessel is a woman. But it – it's – it's more than that. She's not just his vessel.
SAM: She's... She's his friend.
CAS: Yeah. Benjamin would never put her in unnecessary danger.
ISHIM: Me? You were sent here to observe humanity, to watch and to learn. But instead, taking up with a filthy animal. Have you no shame?
AKOBEL: Who are you to lecture me about shame? Humans aren't animals.
CAS: Why do his words bother you so much, Ishim?
ISHIM: Who is he to question my choices? Who is he to question yours?
In Ishim’s mind, humans are base creatures, ruled by their animal instincts. They shouldn’t question angels. The gender stuff is a bit of a red herring for the fandom, because it's ACTUALLY about the human-angel divide and how they view each other.