There are several points to consider:

No one can confidently say what should and should not have been included in the bible since it was supposedly put together by a number of priests how can we be sure that some texts were not deliberately left out.

The gospel in question was written in ARAMAIC not ARABIC there is a clear difference.

To say that the Quaran is the only religious text containing violence is also untrue, people were killed by the instruction of God in the bible also, those who are unsure sure read again closely!

All those confidently pronouncing the bible as the only true text and including facts about when it was written and by who have no real evidence to back this up other then their FAITH. This faith is the same thing that binds muslims to believe that their religion is the truth so you cannot criticise the teachings of one religion without being a hypocrite.