Sam gets that a lot of other people think things like college and a stable place to live are boring. A lot of people do it and wish they could be doing something more exciting - even people who don’t know about hunting or what’s out there in the dark. They join the military, or they jump of planes or off cliffs with elastics strapped to them, or whatever. It takes a certain kind of person to want to hunt, and there’s a lot more of them out there then the ones who actually hunt. And that’s fine, someone needs to do it - someone has to, or else they’ll all end up dying. But that doesn’t mean Sam wants to.
And he’s having a hard time imagining Jo hunting, not because he doesn’t think she can but because he can remember too clearly the way she’d sounded when she was terrified and hurting, and he knows that hunting does that to you, often, and he doesn’t want that for her. Sure, she handled herself well - better than Sam did, even - but he doesn’t get why she’d want to go through that again and again with things that are even worse than psychotic humans.
But he has a feeling that arguing with her over it would be like arguing with Dean over it. Some people are born to hunt.
>>“Well you'll be eighteen not much anyone can do to stop you. I mean, I don't know about you but I'm tired of people making choices for me. I'll go where I want and do what I want and if I screw up I'll deal with it. It sucks just letting things happen to you y'know?” He nods, pointedly holds still even though he can feel himself edging back towards shaking again. He doesn’t know what he could have done differently, and that bothers him more than knowing Gordon is still out there - because if it happens again, it’ll go the same way, won’t it? If he can’t do anything, it’ll just happen to him again, him and whoever else is near at the time if Gordon feels like playing more games before he just kills him...
>>”It'd be good to be the one actually doing something.”
...she doesn’t mean that the way he takes it. He knows that, he does, he knows it’s just that he’s paranoid and still has Gordon’s words running through his head, remembers the thrumming power he could feel under the agony while the ritual’s result was going on, and he sort of panics - she’s saying something about parents, and he’s trying to breathe and not look like he’s freaking the hell out (trying to stop freaking the hell out ).
“You don’t.... think he was right about me, do you?” He’s sort of breaking the unspoken totally not talking about that rule, sure, but he’s also really not thinking clearly and it sort of slips out before he has the presence of mind to check it.