Being a sniper is not a nice job, for two reasons.
Reason one is, in the indescribable maelstrom of chaos that is regular combat, it's often next to impossible to tell who killed the guys you're all shooting at. It's less traumatic in general, due to the adrenaline and the confusion and the thought that maybe, just maybe, you never actually hit anybody at all.
Snipers do not have this luxury; they see living, breathing people, and they make them dead. It's a hell of a thing to realise that the guy you just shot through the neck was showing a picture of his little sister to the guy next to him. What's worse is when you don't kill the fuckers clean, and they're rolling around on the floor screaming their heads off, or crawling back towards their friends begging for help. Then you're faced with that horrible decision; do you finish him off, pop one through his skull while he can't duck out of the way, and send him home in a box? Or do you just leave him there, drowning in his own fluids as the medics refuse to go near him because they're afraid you'll punch a hole through their lungs too?
The second reason is, of course, related. The Geneva Conventions don't apply to snipers. They're supposed to, sure.. But when Jimmy kicks down the door to your nest and aims a gun at the guy who he knows for a FACT just obliterated the face of his best friend since high school, well.. Let's just say it's awfully tempting to just pull the trigger and claim you went for your gun.
The friendlies hate you because you're a skulking coward who is emotionally distant at best, and a psychopath at worst. The enemy hate you because you are someone they CAN hate, someone they can actually link all the pain and death straight back to.
Being a sniper is not a nice job.