Quickscoping was something that treyarch frowned upon I thought? After BO1, they made their intentions known that they wanted to get rid of it, while IW promoted it and wanted to keep it going.
I hated going over my friends house when MW3 came out. his girlfriend lives with him, and she often has her little brother for the weekend. the kids in his mid teens and he's one of those stereotypical trash talkers you hear over the mic. quickscoping is all he does. he runs around with a sniper rifle and when he sees someone, he barely taps the aiming, lets it go and fires. he gets a headshot 80% of the time, before the other guy gets off more than 1-2 rounds from his fully auto weapon
Sounds like he has better accuracy than you and you're mad because you can't do it. What happens when he misses his shot? Does the other guy stop shooting so he can rechamber his next bullet out of courtesy? No, he gets mowed down.
95% of people that complain about quickscoping get destroyed by someone that's good at it, try it for themselves, suck, and then try to get it nerfed because they aren't good at it.