They can't even get along with each other. Nobody kills Muslims better than a militant Muslim. Even the likes of the Wahabbis see 90% of the other Muslims as apostates or infidels, or those that have "perversed Islam" ("bidah") from its genocidal and fanatical 7th century roots. The punishment for this is forced re-conversion or more likely, death.
So even IF these swine could kill off 5 million Jews, Christians, Buddhists, Hindus, Agnostics, Atheists etc, they would be then be obliged to murder their own. Thus Islam is a ideology of permanent persecution and violence.