I would think the same as I did when two men drove a 4x4 into a Scottish passenger terminal. I didn't go out and sell my 4x4.
Other than grounding all private aircraft how would anyone ever prevent a PA28 crashing into the kop end at Old Trafford at 3.00pm pm one Saturday afternoon while the cameras are rolling?
Sure there is a risk, but the risk / reward ratio is what most people are concerned about. Disproportionate mitigation measures are a bigger risk to our 'way of life' than any terrorist.