The important thing to note from all this is that we have to be able to draw the line between having the right to freedom of speech, and having the right to disrespect or make fun of a religion or race. I'm all for being able to express yourself, everyone can and should have their own opinion about things like religion. But when it gets to the point when you know that what you're saying is going to be something that is highly offensive, and can be considered as being racist, to such a big group of people, then I think you are crossing that line. If you have reached that point then I think you are simply doing it to get attention, other than anything else.
Just look at the latest cover of Charlie Hebdo, in which they've depicted the Prophet Muhammad. They didn't NEED to do that, I get that they were trying to show that they aren't going to back down, but they didn't have to depict in that way. There's about a million different ways I could think of getting that message across without using any disrespectful images. Instead of showing that the whole world stands against extremists and such attacks, they have further twisted the knife in the wound and have caused further unnecessary problems.
And in response to what you said about no Christians backlash or attack for making fun of Jesus, I highly doubt that. Maybe we haven't seen it in the news, or heard about anything as big as this, but that doesn't mean that it hasn't happened.