Note that even the description that you’ve provided hints this duplicity: hostility is objective, but “negative emotional” is subjective.
That’s interesting. My first reaction was to think it’s more the other way around. Hostility is based on intention which is in fact un-knowable unless you make assumptions about how patient an adversary is, whereas emotional content has simple litmus tests like looking at frequency of certain words. But, hostility can be seen as game theoretical and mathematical, whereas emotional content comes from an older part of our brain and is only partially shared between people, so I see what you mean. I guess sometimes more subjective things can actually be more measurable, counterintuitively.
I wonder if there’s a good example of a space that’s toxic, as measured by the effect on participant’s mental health scores, but only to some participants. I’m conjecturing that there is not, that at least 80% of the population will experience it the same way, but I could be wrong. I suppose even a very stressful interaction could make someone feel less lonely.