People need to the difference insult and joke. Yes, sometimes a joke might be an insult, but then it won't be called "joke"..it will be an insult. Its not OK with us if someone insult to our belief and prophet. Its not OK with us if someone among us, Muslim, insult other's beliefs. We care when Christians insult Jesus, even though they think Jesus is the Son of God. Here, I don't mean all christians, but yes there are some christians who make fun of Christ...and ofc, some respect him more than anyone.
If you read Da Vinci Code, its said Jesus married to someone and had a child [or children, don't remember much]..which is oppose to Bible, but no Christian seems to dislike this, even this "freedom of speech" is a lie made of "their God"....? (I know, you believe its just a "imaginary stroy, not true"). But in Islam it forbids Muslims to make [false] stories of or fun of any prophet, so we care when someone insults [or say a lie about] prophets [whether its Jesus, Muhammed, Abraham, Moses.etc].. though some don't care when someone [even someone among them] insults their "God".
I'm not saying, burning down buildings, killing innocents.etc is allowed in Islam (infact, it forbids such actions). I know it creates a bad picture of Islam, but if someone really want to know Islam he needs to read Nobel Quran not look at the way "part" of Muslims live.