Why don't we Defend Jesus?

Today Tubby posted about the Muslim world's reaction to the Pope's comments about Mohammed. It's definitely worth a read if you have the time.
The whole thing reminds me of the comics saga earlier this year. I was amazed then, as I am now, at how fired-up Muslims get when their prophet is mocked.
But this got me thinking - why don't we defend Jesus? Every day Jesus is mocked on the radio, in the media, on The Simpsons, and by our friends. But we don't do anything.
Ok, so we shouldn't go running around burning the houses of everyone who disagrees with us. But surely we should be willing to say something!
Tubby says:
"Their aggressive reaction is based on fear. But I refuse to live in fear, for I am a disciple of Jesus and I have nothing to prove. The apostle John wrote:
‘There is no fear in love. But perfect love drives out fear, because fear has to do with punishment. The one who fears is not made perfect in love.'"
And I agree with that entirely. But I wonder, do we say nothing because we have nothing to fear? Or do we say nothing because we fear what our friends will think of us?