Anything is a potential terrorist threat even a garden lawnmower could be loaded with explosives and you dont need much intelligence or skill to drive one of those unless you are trying to get straight lines on your lawn :-)
The difference being that when a lawnmower is packed with explosives and set near the entrance of a mall or public area, then detonated, nobody is going to ban lawnmowers, and the lawnmower industry won't go down the tubes.
What can be done? First of all, take it as seriously as the politicians and the uninformed public does.
In the US, the FAA has had teams that travel about the country for many years who have one job; violate secure areas. For many years, it was as simple as hopping a fence. They would then walk through hangars and secure ramps. Anyone that didn't challenge them or report them was violated. I knew of one group of workers in a hangar that shared a ten thousand dollar fine for failing to ask for ID and report them.
This sounds simple, but much like a police officer giving traffic citations, it raised awareness by enforcing basic practices. I wandered around the world's largest seaplane base a week ago, enjoyed visiting the various aircraft, took in a museum there, got a hair cut. I was there for most of the day, and was challenged by one individual who was keeping heads up and looking for those that didn't belong.
Europe is much better in this respect, and that includes the UK. Fewer airplanes, fewer flying, greater cost, smaller community, but more than you think, as great an opportunity to take an airplane or to do something with it.
The threat isn't to the public at large. The public couldn't care less if general aviation grinds to a standstill. The threat isn't to the man in the butcher shop or the woman in the hair salon. It's to you and I, and security, watchfulness, caution, all come on our shoulders. Not the local constabulary.
When it's among us, the flying community, that the idea isn't taken seriously or fully respected, then there's nothing else standing between public paranoia and the influence of the media to erode or remove our flying privileges or so sharply curtail them as to remove all utility and enjoyment there from. You get the picture. If it's you, the folks participating in this thread, who lightly dismiss the threat, then it's very nearly a done deal. This really is an issue of self-policing. My company; we place security personnel, do background checks, sweep the airplane, yada, yada. But the flying private public? No. I have internal security. I see to it myself as my own role in inspecting the airplane before I fly, etc. But the general aviation community? No. security and the future of general aviation really belongs to you, and it doesn't stand a prayer if you don't take it seriously in all it's forms, benefits, blessings, threats, and failures. It's all on you.
Take it seriously. Act accordingly.