All for one, one for all

Considering the fact that almost all religions claim that there is only one God, and assuming each of them to be correct, we are left with the single conclusion that all religions talk about the same thing or person or whatever. A funny thought came to my mind sometime back, just imagine the laugh this God guy must be having, seeing people fight and kill, with both sides fighting for the same Him(or Her,no offense to the ladies)! That makes most of the world's biggest wars fought with both sides actually on the same side!
Its really hard to believe what things people do in the name of religion and God, but I guess its not their fault most of the times, blind ignorant faith is the easiest thing to manipulate. Someone fights for Ram, other for Allah, someone else for Jesus, yet someone else for Jesus's apparently secret wife, but behind these innocent blank clueless curtains there is true unity, with a handful of people fighting together for power, wealth and all that jazz, not caring, not fearing once while stepping over their own Ram or double crossing their own Allah. Its hilarious at times, pooja water kept in vodka bottles, supposedly "daridra" priests flaunting the latest Nokia N93 handset, and countless other things people are smart enough to hide most of the times.
Why can't each of us let the other be? Why can't everyone look at everyone else just the same? How can we be so blind, so naive, so gullible, so easily manipulated?