I am one of those nervous flyers lol. Having said that I have never stopped a plane from departing and hopefully never will. However I do think that if someone is having a complete wobbly and freaking out and they cant be calmed down or helped then it is the right thing to do for them and everyone else around them to let them of the plane even if it delays subsequent flights. I as a SLF would be understanding if I heard my flight was delayed because of an incident with a nervous passenger, and I think most people would.
Panic attacks are rotten, I have suffered with them all my life, and you never know when they are going to strike! So in that sense it is difficult to pre empt any problem.
Generally though I think if more nervous passengers found out more about how aircraft works and the noises and sounds you are liable to hear etc beforehand then this would help no end. I know it helped me, although on my last flight I was pretty sure I was going to die lol as the turbulence was so bad! However I was wrong and our wonderful captain and crew got us home safely, you are all very talented people in my eyes thats for sure.