What you don't understand, is that I have a firm grasp of the bible as a whole. I spent 15 years of my life as a christian. Went to church, sunday school, private christian school and a year of bible college. So you can stow the condescension.
Jesus is a role model to modern moderate christians. But tell me then how the crusades were justified? How slavery was justified? How the klan justifies their behavior? How those who bomb abortion clinics justify their behavior? And you know that is just the tip of the iceberg.
My point is simple. The old testament, which is not written off by many christians, allows for justification of a whole host of evil behavior. Just as picking and choosing which portion of Muhammad's life you will emulate gives different messages to different people.
Most religions with any success do the same. They are forced to by shifts in culture and world events. When an eye for an eye is deemed necessary you use it to justify everything from self defense to warfare. When turning the other cheek is the wise move, you talk about gods peace and love thine enemy.
If you had had a good understanding of what Christianity is you would not be saying the things that you are saying. The crusades cannot be justified from a Christian point of view. If it wasn't OK to defend Christ using violence (Jesus told Peter to put down his sword when the latter tried to stop the High Priest's servants), then violence is never justified, not even in self defense. However, this is something that not all Christians are willing to accept. After Muhammad's dead, Islam swiftly conquered all of North Africa, most of the Middle East, the Iberian Peninsula, Southern Italy, and large parts of South East Asia. The Muslim warriors of that time had a deep hatred of Christianity. They behaved even worse than the members of ISIS. In the conquered territories they routinely raped and killed Christians in the most gruesome ways. Knowing that all of Europe was about to fall under the Islamic onslaught, the Emperor of the Byzantine Empire asked the Pope for help. Pope Urban II mobilized troops to help the Christians that were being attacked by Islam. The crusades later on degenerated into a bloody, grotesque conflict. So, the crusaders were wrong from a theological perspective, but their initial goal was simply to protect other Christians from armies that were no different from ISIS. Also, Europe would probably have been conquered by Islam if it hadn't been for the Crusades.
Regarding slavery, it was profitable to have slaves, so some people chose to pretend that American slavery was compatible with Christianity. Just read Exodus 21:16 and you will see that slave traders must be put to death according to the Law of Moses. Hence, American slavery was utterly incompatible with Christianity. Of course that some people preferred to ignore verses like Exodus 21:16. After all, there was a lot of money involved.
The KKK is not even near to being Christian, regardless of what they claim to be. If you had ever been a real Christian, you would know this. There are innumerable ways to prove that the KKK would make Jesus puke in disgust. For instance, consider the fact that the first non-Jewish Christian was a black Ethiopian (Acts 8:26-40).
My advice to you is to go back to the Bible and read it. Perhaps you will understand it this time.
