This was something that was actually done historically. The best person to take out a sniper is another sniper because a regular grunt is most likely going to get themselves killed trying to hunt a sniper. Another sniper, on the other hand, has the tracking and field craft skills to hunt down another sniper. This was exactly what was done during the Vietnam War, when the North Vietnamese got tired of Marine Corps sniper Carlos Hathcock killing lots of their troops they dispatched one of their top snipers to take him out. What ended up happening was a life and death game of cat and mouse with both snipers slowly tracking each other in the jungle. Gunny Hathcock ended up winning when he saw and aimed at a glint of light coming off of the North Vietnamese sniper's scope, this is where the movie sniper trope of shooting through another sniper's scope came from.