A good friend of mine is a rocket enthusiast. He comes down here to Beautiful Central Oregon 4-5 times a year and his club launches home-made rockets out by Millican. He used to just do it, like most hobbies. Now DHS demands he jump through a myriad of hoops, tests, fees, licensing... and divulge extensive personal information, and he is now severely limited on how high or far his rockets may travel. DHS will put the same noose around model plane enthusiasts. I personally guarantee it.
As for supposed terrorists flying model planes and rockets into targets in the US...if that ever happens they should certainly be prosecuted. Just as they would if they drive a carbomb through a gate to blow up a building. Or use a Zippo to start a fire in a public building. When bad people are found to be doing or planning bad things there is cause to investigate and take action.
This has nothing at all to do with honest, law-abiding American Citizens or their hobbies. There is no legitimate, legal reason to be compiling these Citizens' names, in fact it is illegal for the government to do so.