Because it's about eternal salvation. If you preach a different Jesus and a different salvation, then people will go to Hell instead of embracing the real Jesus and the real salvation.
The violence and evil in this world is small potatoes compared to the eternal ramifications of false religions.
And which false religion do you belong to?
Here’s an idea to go with your lack of tolerance of other peoples beliefs, just execute anyone who does not believe as you. That will fix your false religion problem for you.
The there's an awful lotta people going to hell, given that the Catholics, the Methodists, the Lutherans, the Presbyterians, the Baptists, the Pentacostals, the Jehovah's Witnesses, ad nauseum, ALL preach different salvations.
To say nothing of course of the Buddhists, the Hindus and the Moslems ! Or....shudder....the Mormons.
Who'd a thunk it ? Only ONE of those groups going to heaven, the rest to hell.
/horsecrap