Alrighty, I'll explain it here to make it easy for everyone.
Firstly, in relation to exploiting, I've discussed this with Pingas, and we are in agreement that it is not exploiting. It would be exploiting if the Helicopter was godded preventing its destruction. However, since the helicopter could have been destroyed, its not exploiting.
Its the same with the RU helicopter being an effective Intel defender, or the tali heli bombing the buildings killing people inside. You can shoot it down (I believe ISIS have rockets do they not), Shooting out the tail also makes it harder to control. It is entirely doable to kill helicopters / vehicles. If tali had no way of taking down the heli (I.E The heli was godded, tali having no air capacity etc) then it could be unfair, but considering tali can legit spawn little birds that can launch rockets that can take out helis, you have an effective counter measure, use it.
There are many things in the game that don't "make sense in real life" however they occur still (Like Tali/Civs sitting outside the main gate at a hostile area).
Taliban have other methods of getting cash / levels, as do every other faction. We can't nerf or prevent other factions getting stuff because a faction doesn't like it. It would be like a rule being brought in preventing Taliban from continuing the raid the base once the intel has left the base etc.
Not an exploit, currently allowed within the rules.