Why are Muslims staging violent protests against Danish cartoons depicting Mohammed? Would you be upset if the cartoons depicted Mohammed as a pedophile, or drawn as a pig, or being sodomized by a dog while praying? That’s what one group of Danish Muslims is showing to protesters in the Middle East to inflame the protests. Just one problem: these three cartoons are fakes that may even have been made by the Muslim group themselves.
The actual cartoons while they can be offensive are somewhat milder. Perhaps the most offensive one depicts Mohammed wearing a bomb as a turban. Many of them only run afoul of the prohibition of depicting Mohammed because it would promote idolatry. The original reason for the series was in response to the problems in making a children’s book about Mohammed, and the fears that such a book would result in complaints of idolatry. The cartoons were meant to satirize how a simple image of Mohammed could spark violent protests. It is ironic that some Muslim groups have reacted to cartoons about violent protests over drawings by staging violent protests over drawings.
So in case you were confused about the reasons for the protests, that’s it in a nutshell. For more:
Muhammed Caricatures by 
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Jyllands-Posten Muhammad cartoons controversy on Wikipedia