Well, it's pretty simple logic that if there's no show, there's no shooting at the show, because there was no show.

As to why this would inspire a Bataclan style shooting at a concert like Eagles of Death Metal had, who knows. Though it's not exclusively America, the shooting I referenced above happened in France. The French do also have nipples too though.

You kind of answered your own question there. People can be unstable and crazy sometimes. Tenacious D will likely resume their shows after the election once things have calmed down. Given enough time, people will hopefully forget about this moment and move on.