why the followers of common prophets fight among themselves ?

i am astonished that jew, christianty and islam have common prophets not one but as many as 25 in numbers, right from ADAM TO HAZRAT MUSTAFA. even then they still have enemical attitude towards each other even in 21st century.even as per the islamic jurisprudence inter-religion marriage is permissable, that means in other words 'ROTI - BETI ' RELATION IS ALLOWED then why the conflict ? all the terror eminates from the hatered towords eachother on religious ground. Does the conflict relates only to the Jerusalam being under the the control of Isreal or their is something more ? perhaps the military strength of the christian countries terrifies the islamic nations or their advancement is point of jelousy for the muslim population ? these questions have to be aanswered truthfully and not diplomatically, as is being done. perhaps the poverty of muslim countries is basic reason of whole dilema , it is like having a hut adjecent to palace. which becomes the reasonof heart burning . in that case the violent movements too have the same reason ffortaking the gun in the hand. whether it is maoist movement in nepal or india, likewise IRA . But one fails to understand that RED army or similar other terror groups or fighting for which cause. I invite the viewers their opinions on this issue.