"Are we too comfortable living in our safe modern society or what?" I think that about says it. The safety and comfort that [most of] our generation [in the US and other countries without a war on their home soil] enjoy is severely taken for granted at the risk and danger that the act of war influences on people.
To be young, and as you say, "won't ever have a chance to prove that" pretty much sums up the naivete and the misunderstanding of what it really means to be in a war... and not playing something trite war simulation game or watching a movie/anime and pretending to understand consequences of doing so in reality.
PTSD and other trauma induced psychological symptoms of war, both as a soldier and even as a victim, isn't something to be taken lightly, especially trivialized as being over reactive or "over sensitive". And perhaps, as with any issue not experienced first hand, it's always easy to just brush it off with "get over it", which is probably the worst thing you can possibly say to someone afflicted with a problem.
Yes, so this type of misunderstanding is indeed very annoying.