Spawn raping is BF is a non-issue, spawn somewhere else. And if you have nowhere else to spawn, glory be to the other team for winning through to such a condition.
The thing with BC2 is that while BC2 AA is nerfed to hell, the tanks coaxial MG can actually damage choppers, the BF2 coax cannot. Also the top mounted machine gun on tanks is much more accurate than in BF2, both of them together can hurt the chopper bad. Plus you got people tracer darting the chopper, that hurts it too. The fact that the tank and its top gun also have both tracers and optical magnification to help them see where they are shooting at long range is helpful as well. And then there's the very fact that the chopper has an altitude cap and there is (virtually) no fog of war for almost the length of the map, letting you engage it as long as you have line of sight.
But sometimes, you do get a good chopper crew that circle strafes well enough that you think, WTF, this aint BF2?!?!