"In fact, the very existence of one of those three religions is an insult to the other two"
In some communities around the world, combinations of Jews, Christians and Muslims live side by side without any problems and with much mutual respect. I have myself seen this with Muslims and Christians in Southern Senegal (Casamance) for example, and also among all three in Casablanca, Morocco. As I've often said on Mudcat, my husband is a Muslim and I'm a Christian, and we have no problems with this whatsoever.
Free speech is vital, but there have always been blasphemy laws, and more recently 'incite to hatred' laws, to take effect where mutual respect breaks down.
A few months ago, there was a birth-control poster showing the Virgin Mary looking at a pregnancy test. I was rather taken aback, as were many Christians, but no-one was attacked because of it. I do feel that it should have been banned however.