You're sticking to this absurd mindset that 40+ people in their 30s are naive, dumb as a rock and unable to think 3 seconds ahead without intuition as to what might happen in a CRPG game that is ALL about its incredibly rich story and wide variety of choices, when Larian has already proven even with Early Access that they are not holding back any punches in terms of the story and how far it can go in any direction the player chooses.
People aren't as dumb as you're trying to convey, at least not those as I've recognized some of them while I was watching. Everyone in that room knew very well what to expect while they were asking for the first dialogue choice, especially due to Sven's responses and laughter. Do not mistake their reactions for innocent ignorance.
As for you thinking it's bestiality, it's simply not because Halsin is an Elf Druid and remains a fully sentient Elf even when he shapeshifts into his bear form. He ain't a real animal and screwing him is no different than screwing a Centaur, a Harpy, a Succubus, a Succubi, a Werewolf, a Sphynx, a Mermaid, a Medusa... etc... take your pick of various sentient mythological beings that are a fully sentient humanoid with animal appearances.
These types of overreactions I've seen in the real world as well, against partners of those suffering from extreme dwarfism that leaves them looking like kids. Despite people suffering from dwarfism actually being even more mature and intelligent than your average Joe, this does not stop people from condemning their husbands/wives as extreme pedophiles and trying to start lynchmobs against them, just because in their programmed brains TINY SIZE = KID.
