Nearly every significant philosophy, including many that are secular, such as Buddhism and Confucianism, has expressed the basic thought of treat others as you would wish to be treated. Follow that. The rest is just invented, obfuscation, justification and dogma.
I am a big fan of Sam Harris and the late physicist/philosopher Victor Stenger, Stenger's God - The Failed Hypothesis lays out all the reasons and physics explaining why a god is neither likely nor necessary. His reasoning is flawlessly logical and supported by the science.
I am a hopelessly logical and evidence-based thinker - I am Asperger's. But if people want to believe in something "out there" as Jefferson observed it neither picks my pocket nor breaks my leg. A lot of believers are peaceable and reasonable people who try to live according to the above maxim. I spend zero time worrying about those people. But many others are not.
The inescapable problem is that the "holy books" are all soaked in the blood of innocents, non-believers and other-believers. Exterminating those inconvenient folks as a matter of purifying and propagating the "true faith" is woven into the woof and warp of those books. Which will provide justification for religious war as long as those books are looked to as some authoritative guide to the way humans should act. It is time to move on.