by that logic, there are no christians, only other pagan sects, being that most the stories in the bible were rewrites of pagan stories right???
Nope. Logic fail there. Maybe if I abstract it you can see past the blinding context.
All Blargs are Blorgs. Therefore there are no Blorgs. T/F?
See how easy that one actually is?
Jews, Christians, Muslims all believe in the same God; the God of Abraham. And all three religions link themselves to Abraham by a different lineage. They are indisputably different branches of the same religion.
All three believe in (what the Christians call) the Old Testament, and the prophesy of the "Son of Man" who is implied to also be the Son of God, though never named as such, and who is the "Messiah" and brings about the forgiveness of Original Sin.
Jews believe that Jesus was a Prophet but not the Son of Man and not the Messiah. They're still waiting for the Prophesy to be fulfilled.
Christians believe that Jesus was the Son of Man, the Messiah, and that his death fulfilled the Prophesy. They also believe there have been no new Prophets since before Jesus.
Muslims agree with Christians entirely about Jesus being the Son of Man, the Messiah, and his fulfillment of said Prophesy. They also believe that there had been one additional Prophet since then, Mohamed, the Seal of the Prophets, who was not divine at all but merely a human man who was chosen by God for the job of Prophet, and who was given a large set of rules to complete the teachings. The idea is that humans weren't ready for many teachings yet at the time of the Prophet Moses, who is also highly revered by Muslims, Christians, and Jews alike. Jesus fulfilled the Prophesy, but left precious few new rules for how to live and how to structure a society based on the principles of Scripture. So there was a rules gap, an information dearth. The Seal of the Prophets brought a final teaching, to tie all the disparate teachings from the past into a single, comprehensive, and final set of rules. So to Muslims there can be no new Prophets.
An interesting example of this is the Muslim image of the "end times," which in many ways is similar to mainstream Christians. In it, Jesus goes out in the world to raise the dead and fly through the air blasting demons with lighting bolts. Mohamed can't do that; he's a human man, given the most important job in history, he has no physical capability to commit Miracles or fire lighting bolts, raise the dead, or battle demons. The see Jesus on the Right Hand of God, his True Son, and the one fighting the devil in the flesh; and Mohamed they see on the Left Hand of God, his esteemed General, giving orders to the field solders from Heaven. He can't leave Heaven to fight in the flesh, because he's Human, and dead. He has no Earthly body to inhabit, only his Spirit body in the land of God.
I'm secular and not part of any of these sects, indeed my meta-physics are more logical positivist, but it is worth knowing the major beliefs that people hold in the world around you.
It is really worth understanding also that the Muslim prohibition on images of Mohamed is not based on perceived insults to him; it is actually based on what Jesus said; "do not call me good; only God is good." Images lead to veneration, and Prophets are not to be venerated; that is the path of idol worship. Not even God's own Son may be praised! All praise must go to God, all veneration must go to God. So the people getting upset a niche group not well supported by the theology whose name they adopt. Also, the strict parts of Sharia explicitly only apply in the perceived Muslim Nation; they do not have their root in commandments for all humans to follow, they are things that community was commanded to follow and implement in their own areas. So it is theologically reasonable for Muslims in Saudi Arabia to impose strict Sharia. But it is theologically not supportable to engage in violence in non-Muslim lands to enforce a prohibition on veneration of Prophets; and indeed, sarcastic and insulting cartoons are poor examples of veneration.