That is not the teachings of Jesus that started wars.... politics/envy/greed started wars.
the teachings aren't what matter. people don't fight over the TEACHINGS of christ, they fight over the factuality of christ or the devotion to christ. it didn't matter what he said.
when two factions war against each other, for example a 9/11 hijacker climbing into an airplane getting ready to attack, he wasn't thinking "you damn judeo-christians, the 6th amendment says thou shalt not kill except when one of the other commandments is broken, not as a sweeping statement for all situations!!!"
they fight because they believe that they know exactly what their god wants and if you aren't doing it you're turning your back on their god. they fight over the "honor" of god. if the qu'ran and the bible were the exact same book, save for the substitutions of jesus/mohammad and god/allah, islam and christianity would still be at odds because each would believe that the other is rejecting the "one true god".