You might enjoy reading the Koran even though it is slightly different from our beliefs, it would be wrong to call it evil.
I've read it and yes it is evil.
GSA(P)
And you are missing the point that the bible explicitly states that through one man sin entered the world. For all have sinned.
God's mercy and forgiveness are abundantly shown in that while we were yet sinners He gave His only Son for us. But if you don't accept the Son you also can't receive the forgiveness.
God operates according to a strict covenent. Once He makes it He won't break it. The covenant He made with mankind is that only a live can redeem a life. Since the wages of sin are death, once someone sins they are counted as dead to Him. Only another death can restore them. So God gave the Israelites animal sacrifice to pay for their sins. But they couldn't even live up to that law. Then God gave His Son as the perfect sacrifice, once and for all. But if we don't accept that sacrifice as payment for our sin then we are still in our sin and are dead to God.
The mohammedans refuse to accept Christ's payment for their sins. They are dead to God and the Father weeps over them.
GSA(P)