Sniper is a part of an team. You agree with your team to achieve base B, so you go with them to base B, get yourself a good place to watch base B, warn your team members marching forward of incoming vehicles and enemy players, care to guard your team members from enemies, and in case that your team gets wiped out, you can be used as respawn-safe point to reach base B again in a rather short time.
Campers are the ones, not involving themselves into what goals your team want to acchieve next, and shooting on unrelevant enemies, while their teams try to acchieve relevant goals and camps for winning the game, while being 25% handicapped for the idiot being 8 km somewhere else shooting at actually unrelevant enemies.
To take the example of the threadstarter, with the polish army. An army is an team, and if you are caring for your team members and orders, as they do, then you are a sniper. While if your army team members would be in a brawl with enemies, asking you for backup and you´d answer them "Oh sorry guys, but I am actually 5 km somewhere else and shooting at some enemy guys eating lunch, because I know that in this spot there are always many unaware enemies eating lunch," then you are an idiotic camper. ^^