If we all only used the roads for ambulances, fire engines and police cars and general emergency use instead of all the unnecessary activities we use our cars for, think how quickly we would see the police or paramedics in times of need and the speed at which they could get to us.
As other's have said, they reject modern living in a general way and to differing degrees from indivdual to individual.
I m just glad that the police did get there quickly. According to news today, what the guy had planned was far worse than what he actually did after being disturbed by the police.
I also think that it is a credit to Amish community that they did accept help in the extroadinary circumstance. JWs as you have pointed out, don't step down or act sensibly when the situation is dire, whereas the Amish community, while the intricacies of modern living are not their personal lifestyle choice, they had an extreme situation, and behaved sensibly and called in the appropriate forces. Not a double standard, just very sensible.