It is simply to easy to judge Christianity here.
Also one needs to define insult, if insult suggests that all Muslims are animals, then sure that is wrong, if insult criticises the religion of Islam, its faith and book, then such is not insult but normal criticism which is applied towards everything. Unfortunately, criticism that is utilized in history e.g. against the Christian faith is labelled as insult, islamophobia or racism if applied upon Islam which is ridicolous.
Anyway we need to consider some history here. If you go back say, 15 years, Christians were not engaged with such debate against Islam, instead Muslims brutally attacked the Christian faith by all possible means possible; I remember it, and I remember how these Muslims, their debators and literature insulted and despised in the most hiddeous way what I found precious.
In the 1980s one Christian scholars, Anish Shorrosh and Palestinian Christian, began to reply back and ask similar questions, these same Muslim debators could not take this pressure and tried to kill him twice and he was badly persecuted for daring to even respond in a effective manner, their attempt to kill him is even one video and can be ordered (let me know if you are interested to see it).
At time I would never debate anyone, as such was unknown to me. I remember in 1995 while at Bible college that I twice suggested polemical approaches in which fellow Christians reacted with anger against me for such thinking; I cannot therefore say that Christians have been anything but polite, patient and tolerant.
Prior to 1995 Christians in the West typically did not attack Islam or criticise it, if anything Christians shared their message with Muslims, however, initially Christians got fed up with the criticism and decided that the Muslims needed to taste their own medicine. This decision launched a range of Christian apologists into war with Islam, so to speak, through which the website answering-Islam.org originated.
What am I saying then, I am saying that the Christian criticism of Islam is simply a response to decades of Islamic criticism and insult of the Bible and Christianity.
Furthermore, that this criticism is necessarily insulting is not an issue, we criticise everything in this world, politic, culture, drama, lifestyle and Christianity, we do not necessarily call this insult, but criticims of Islam has been phrased as insult rather than criticism, and many seem to follow this trend, as if Islam has the only monopoly upon being secured from criticism.
Furthermore, go to any Islamic country and consider the freedom of speech, in Pakistan for example Christians are being daily criticised and insulted through media, papers, television etc, and they have not even the permission to reply back or defend themselves; the Muslims have attempted the same in the West but here we respond.
Let me also add that most of these Christian apologists were born and brought up in Muslim countries, were they experienced Islam first hand, they faced such insult for years, and even persecution.
Call it insult anyone, but then lets end all insult, or criticism toward anything, even Christianity, and that will not be accepted. Its amazing that now when Christians start replying we need to consider tolerance, peace, behavior, and of course we need to apply these and criticise in a godly and mannered way, but why was this not urged before 1995. This would have avoided the present situation.
Or lets keep the debate going.