1. It would be wrong to burn Korans.
2. It would be wrong, when a handful of idiots in America burn Korans, for Islamic people to attribute that to the hundreds of millions of Americans who would never do such a thing.
3. It is wrong for Americans to be fearful of retaliation; there would be no justification for retaliation, and one cannot live one's life in fear of unjustified behaviors. One can only counter them when they occur.
4. While the people doing it might be Naziistic, there is a big difference between these planned book burnings and those of the Nazis. Nazi book burning was done with the approval of the government. These book burnings would be by a handful of rightwing nut jobs who are opposed to the government of the United States.
5. As to preventing this.... you can't. Even if the nutjob who threatened to do it changes his mind, there will be others stepping up in his place. This is America, which has a large degree of tolerance for bad behavior. Our jurisprudence allows all kinds of vermin plenty of room in which to demonstrate what they are.