It's actually not a question of faith at all. Faith is personal and spiritual.
Although it may seem, on the surface, that faith causes wars/unrest, the truth is somewhat more complex. Humans have an in-built herd instinct and a need to feel secure as part of a wider group. Often, religion is a handy tag, but dig deeper and you'll often find that many of those who claim to be religious have little if no concept of the detail of the faith to which they apparently adhere.
In reality, many humans seek like-minded souls for security. This can often be, at a local level, support for a football team . You only need to look at Rangers and Celtic to see this at work. However, it's got sod all to do with faith. There are just as many "local derby" matches, at which the enmity between fans cannot be attributed to faith. Equally, the violence in the Uk in the 1950s between Mods and Rockers was between groups who felt that their gangs (= their security) was being threatened by others.
From a local to national level, we can see that neither WWW1 or WW2 was instigated through religious rivalry. In the case of the former, the leaders of Serbs and the Austro-Hungarians were rivals for power. In WW2, Hitler actually tried to sideline religion and merely used the danger to the security of the Arian race posed by gypsies and Jews to bind people together in the fight to maintain their apparent security.
What I am saying, albeit in a late-night long-winded way, is that blaming religion as a cause of strife is a cop-out. Even if there were no organised religions or faiths, humans would still find a way to bind themselves in groups and fight to protect their groups from perceived threats from other groups, however notional/imaginary.