You make good points about comparative psychology, it does seem like we use the way other people react to things as a barometer for how we react - including how loudly to complain or how long to linger on an injury.
Although I think its less extreme than you paint it - really extreme trauma like rape or murder shouldn't really be desensitized, it makes sense to be devastated when something horrible happens.
Small stuff though, I think social media and the internet are making it a lot more stressful for everybody.. so much easier to compare to each other.