Sincerely Christian  

An introductory word of explanation

As a Christian I believe that the God of the Jews and Christians is the only true God who created all things in heaven and earth.  I believe that God became a man in the person of Jesus Christ and by His death as a perfect man paid the penalty of mankind's rebellion against Himself.  Although Islam is a monotheistic religion, they do not worship the same God; the god of Islam is the moon god, as their crescent moon symbol indicates. 
 
I have many friends and acquaintances who follow other religions or none.  I respect their right to hold their own beliefs: freedom of religion is a basic human right.  Adam exercised that right when he disobeyed God in the garden of Eden.  So you can see, freedom of religion is a right, but it can have dire consequences. 
 
So, although I value my non-Christian friends and respect their right to follow another religion or none, I sincerely believe that they are wrong.  In fact, I believe that they are sincere, but sincerely wrong.  Sincerity alone is not enough. After all, if my God created everything that is then anything else that claims deity must be either an impostor or an inferior being or a man-made substitute.  In fairness, if others sincerely hold their beliefs I would expect them to say the same about my God. 
 
As a brief aside, in Genesis 20 Abraham had lied to the Philistine leader Abimelech saying Sarah his wife was his sister, and Abimelech  took Sarah into his house.  Now the Philistines did not worship Abraham's God, they worshipped Dagon, a fish god.  However, when Abraham's God spoke to Abimelech in a dream, the man did not argue about whose God was greater.  No, he did as he was told! 
 
One reason was that in those days there was still a remembrance of the one true God even though other gods were worshipped.  Another reason was that Dagon never intervened directly or spoke to anyone in this way, so Abimelech knew at once that he was in the presence of a greater Power.