I'm normally against this sort of thing on principle, but I think there is actually a legitimate concern when it comes to rockets. The only real difference between rocket technology and missile technology is intent.
This said, I think we are approaching an era when the publicly available rocket science becomes "good enough" for effective missile use, rendering continued restriction pointless. Currently the North Koreans have some serious trouble getting stuff up there (a single satellite, orbited very poorly), so the restrictions for rockets actually seem effective, but once they've figured it out (and it is only a matter of time), then I don't think there will be much point to continued secrecy. It would kind of be like China trying to keep the silk worm under wraps today. That cat is out of the bag.
I don't know how much rational arguments enter into it.
The U.S. State Department has consistently avoided going to court on ITAR questions, because some of its pronouncements seem clearly unconstitutional. They'll never let it be tested, though.
There was a case where a civilian IMU, or some-such was used in a civilian aircraft and then later used in a military missile. Because of the missile use, it fell under ITAR and the U.S. aerospace firm that was using it in the civilian vehicle was fined. This seems like a retro-active law which is unconstitutional. It was easier for the firm to just pay the fine, rather than litigate.
I'm lazy, and this is anecdotal, but this story seems to be well known in new-space circles.
This said, I think we are approaching an era when the publicly available rocket science becomes "good enough" for effective missile use, rendering continued restriction pointless. Currently the North Koreans have some serious trouble getting stuff up there (a single satellite, orbited very poorly), so the restrictions for rockets actually seem effective, but once they've figured it out (and it is only a matter of time), then I don't think there will be much point to continued secrecy. It would kind of be like China trying to keep the silk worm under wraps today. That cat is out of the bag.