Micro:
That 3,000 ft launch on an L is straight up. At your 40 degree launch angle, that thing augers into the ground barely a few hundred yards away. Again, we come back to the reality that for a foreign terrorist, it's easier, more reliable, and more effective to get an earlier generation military rocket to do the job than to make and detonate a hobby rocket, or, if we're talking about a football or baseball game, a box truck loaded with fertilizer and kerosene. Even an R/C plane is a more effective delivery method (sorry to the R/C guys, but it's true). Also, again, we're talking about small J motors here in the legislation, not even L's or M's.
The other problem that occurs if you're trying to create a homemade rocket is the issue of creating an explosive that a) won't detonate when you launch your rocket and b) will detonate when you reach your target. Most homemade explosives are too sensitive to survive a launch and if they're not, you have the problem of effectively detonating them at the right time.
Oh, yeah. By the way, Semtex is about 140-150% TNT, IF you get it to detonate effectively. That's just not as easy to do as you imply. A 10" diameter capsule is the most effective container. The rate of the explosion goes down the narrower your container gets, so your more streamlined missile becomes less effective. Besides, if you're looking at the cookbooks to make Semtex, you're also probably have the wherewithal to make your own motor (it's in all the same cookbooks). If anything, allowing someone to buy hobby motors makes it more possible to trace the possible end user of the motor.
9/11 and the OKC bombings occured as they did because in both cases the terrorist chose the most effective way to cause the most havoc possible with the greatest chance of success. A hobby rocket just doesn't fit that description.
The real issue is that APCP is being regulated as an explosive, not as a fuel, while it is a fuel and not an explosive. As such, it should legally require separate legislation to outlaw it. If your argument is that it's a delivery vehicle, then it doesn't even belong in the ATFE's basket, nor does it belong in the SEA.
Yes, we are in the minority, but freedom or the lack thereof shouldn't be legislated based on the number of people whose freedom is compromised. This is where we ended up with segregation laws and the Japanese internment camps in WWII, and this is why there are a dozen better delivery methods that will continue to go unregulated. As long as it's only a small group of people, their rights and freedoms are inconsequential. As long as you don't trample the freedom of at least one percentage point of the population, you can go right on ahead.
Also, it's as Doug said. We can't ban substances based on potential abuse of these substances. If this is the case, we have to ban fertilizer, any petroleum product, or firearms in general. This is precisely why the ATF's Congressional mandate on explosives states "any substance who's primary purpose is to function by explosion".
I now have a friend about 20 miles away who has storage he's willing to let me use as contingency storage, so I will probably do my hoop-jumping one way or the other before next flying season so I can get down to business to fly my TRF rocket on a K again (this time hopefully successfully) next spring or summer.
It *is, however, absolutely silly to say that my H or I motors that I'd like to fly locally in the meantime are potential terrorist weapons. I think the legislation that exempts up to small J motors is a very realistic and well reasoned compromise between the need for "perceived safety" and the freedoms of rocketeers, and not "crazy" as the Senators would suggest.