A weapons effective range is limited by its red reticle range. Scoping in increases the range, out to which, the weapon receives red reticle.
The penalty for being shot while in scope is a reduction in effective range, not actual range, and certainly not the ability to aim.
The penalty for being shot while in scope is absolute: the player is descoped; nothing more, nothing less. Not only do the effects of the Flinch mechanic, to what degree a targets aim is disrupted, vary from weapon to weapon but those effects are additive rather than absolute. Simultaneously being shot by two enemies will disrupt the targets aim twice as much; players can only be descoped once.
The ability to ping a sniper, in order to remove him from scope, allows a player to take away one of the Sniper Rifles greatest advantages: the high magnification scope and accompanying increase in red reticle range. While a player may not be able to kill a distant sniper with a utility weapon, he can reduce the ranged damage that the sniper can effectively deal by forcing the Sniper Rifle into reduced aim assist mode.
Flinch makes Sniper Rifle bodyshots overpowered. There is no point in going for the, more difficult to achieve, headshot when one Sniper Rifle bodyshot will have the target unwillingly staring at the sky and unable to return fire in a timely manner.
Flinch makes shots against a scoped in sniper underpowered. Instead of removing the Sniper Rifles long range aim assist and high magnification scope, the snipers reticle placement is ever so slightly disturbed but no where near enough to be an effective deterrent.
When the penalty for being shot, while in scope, is being removed from scope, it creates a self solving problem. You are scoped in on a distant enemy. The enemy does not want you scoped in on him. He descopes you. Problem solved for him. Alternatively, you are scoped in on a distant enemy. You are then shot by a proximate enemy. Now you are the one who does not want to be scoped in with an enemy so close. You are descoped. Problem solved for you.