just as a small nitpick
Just as a small nitpick,
1. The mentality that most fights happen under 300m isn't really a Cold War era idea, but also why WW2 used SMGs. And not just the Schmeisser; the Russians produced far more of their own burp-guns, the Brits produced quite a few Stens, and the Americans developed the grease-guns because the Thompsons were too expensive and slow to produce for how many the army wanted. Also why it culminated with the invention of the assault rifle.
But even WW2 didn't produce that idea. The Thompson itself was born out of a WW1 need for a "trench broom", i.e., something to put a lot of bullets in the air at close ranges.
2. The designated marksman rifle isn't just for short range sniping, or it would be a bolt action rifle for maximum accuracy. It's also for suppression. Psychologically, a "sniper" ranks up there with heavy machineguns for suppression factor.
3. Calling "snipers" murderers is at least as old as the American Independence War, where brits with muskets without sights (not that you'd have use for sights on a musket, given that the only way to be hit by a musket ball was if it was aimed at someone else) called the Minutemen murderers for having rifled guns with iron sights.
I guess it's just that most people have this aversion towards killing someone personally. Probably more people got PTSD ("shell shock") because they shot someone point blank, than because of being shelled by MLRS.
That, in turn, is known at least as early a the Roman Legion. The Romans rotated ranks in the middle of the battle, so their soldiers wouldn't get a nervous breakdown from all the killing. For all the willy-waving about being the sons of Mars and all that, when push came to shove, even for them it was pure stress.
The aircraft and airstrip crews, and often even those soldiers with assault rifles and machineguns, have an element of plausible deniability. You can lie to yourself that maybe it wasn't your bullet that killed that guy, or maybe those kids in that bombed school weren't hit by the bomb _you_ loaded, etc.
Or if you will, it's why a few weapons in almost all firing squad were loaded with blanks. Even though anyone who's fired a rifle can tell the difference, each soldier can still lie to himself that _his_ gun had a blank.
Or if that doesn't work, you can convince yourself that it was self-defense. That guy was trying to shoot you, so you shot him first.
What I'm trying to say is that the loathing of snipers doesn't necessarily have anything to do with numbers of kills. It's got to do with knowing that someone can calmly look you in the eyes (through a scope) and squeeze the trigger. Even if you're no danger to him, due to different weapon ranges. And then he can do it again. That's unsettling people.