First of all, I don't feel SPN needs to be defended. Perhaps the people it's phobic towards need to be defended more. Second - I'm no expert on the topic, but as I understand and experience it - perpetuating a hurtful and harmful stereotype is very much not the same as saying a similar thing about someone the stereotype isn't used against. In SPN terms - calling Sam a monster is a way bigger deal than calling Jess the same thing (probably), since Sam experienced feeling like a freak his entire life, was persecuted for it by heaven and by other hunters, even, and himself feels that he not OK because of it. Assuming Jess didn't experience any of those things, it would probably be way less of a big deal for her to be called that. Especially since there were other stereotypes there as well. In addition, SPN made a point of going on and on about how angry he is. Just like his father before him. And he wasn't even, so we'd like him. And the gunshot in the end was framed to be considered unexpected, if not surprisingly violent. He didn't even get to have the justification of having to do that to save someone on the spot.