Y'all are looking for impact-injury realism on a show with sentient androids, clones and DisneyWorld for psychos. Really? I think this is just one of those things you have to accept within the show's internal logic. A logic that states that hosts can't hard guests....much.
This is what I meant a few weeks earlier by "people won't accept another LOST". The zeitgeist has changed, and is changing rapidly (look at US 'belief in evolution' graph). People now expect rules to be set and actually govern the depicted diegesis. The whole 'oh you can knock someone out without damage' is one of those now increasingly archaic relics that can longer be used so liberally, since we all know now (and can pretty quickly be pointed to) that head injuries are more likely to have lasting effects than a lot of other injuries.
Additionally, it's a weak writing exit to either hide information or create artificial emotion stakes where none exist. Video games like Crysis 3 do this almost every other level because the writers didn't know how to connect dot A to dot B. I remember that game very specifically pissing me off on that end. But movies and shows where the writer can't write a decent exit tend to pull that a lot too. I haven't kept count over the years, but I'm fairly sure the Winchesters in Supernatural don't even have brains anymore from being knocked out so much.
I will give the show the benefit of the doubt there because it was shot in 2014 (before The Martian's success, I guess), but between the sudden jump in grounded realism of The Expanse and other shows (the actual language of the Dothraki in GoT and another in Defiance, despite being the same guy responsible) and science education apparently going up (I suspect Youtube plays a part there), there is no more room for fucking around on a sci-fi show if you want it to be high-concept. Either you go all the way or you stay home, but that's how it's gonna be from here.
I mean, we have deep learning machines now that will likely be credited for discovering the 9th planet (or brown dwarf, whatever it will turn out to be) when applied to astronomy and the search for that now fairly certain body of mass. We have self driving cars, an end to most jobs, and other things. No show that still plays by old-fashioned rules is not going to stand out like a sore spot when the future drives by you every other day. People adjust quickly, even if they don't realize it. That's whole point of a cultural zeitgeist: you can't capture it, predict it, calculate it, or return to it, but it's there as a distinctive part of a unique place in time.
Of course, the writers could argue this argument in reverse too: being knocked out may be considered part of the Westworld experience. I don't think that's convincing, but they could hand wave it away by saying that brain damage can be repaired in this future. Buuuuut then you got yourself another problem, which is that death can be repaired too, eliminating Arnold's death and the entire threat of it for humans. So that's not an option. The better thing would have been to avoid the issue altogether.
I'm all too aware of the writing frustration of discovering that a central pillar doesn't work because of 'science thing x' when you just build the whole story on top of it. The real question is of course whether you've drawn attention to it. In Westworld's case, they unfortunately have by saying there are safety rules, but rarely putting them into visual action so that the viewer would have an understanding of how they work. Can't have that cake and eat it too.