To be honest, all your other arguments for quickscoping are mostly bullshit.
Although, there is one last part at the end of your post that completely redeems and validates your argument.
"Why should sniping adhere to real life while using an assault rifle and other guns don't adhere to real life?"
That pretty much sums up CoD and your argument for me and it's a completely normal argument.
for example, shotguns in CoD have a range of barely over a few feet, wheras in reality a normal 00 spread will have an effective range of easily over 50-70 metres.
Assault rifles (and all other guns) actually need to be aimed over distance and an assault rifle's spread doesn't magically change from a few centimetres at 10 metres when aiming to over a metre when firing from the hip.
So why should sniper rifles be constricted to things like this? As far as I can tell, quickscoping wasn't even that big of a deal in the last game, just a subculture of gamers who play that way.
Anyway, my incredibly tedious and dragged out point is, if no other gun in the game has to behave like the real world equivilant, why should sniper rifles?