You're right about the whole tribalism thing but do you really mean to say that fundamentalists / extremists don't give moderates a bad name?

There's a difference here; moderate muslims (for instance) and extremist muslims all march to the beat of the same drum while atheists have no drum. Muslims are all alike in that they hold the same book to be holy. Sure, they're different in plenty of other ways but they all have that one thing in common.

In cases like those where a mother will kill her children so that they can go to heaven, it is a wrong done by one person which is indicative of the faults of the whole group. Suicide bombing is an even better example; it takes only one person to load up on explosives and flip the switch but it wouldn't happen if it weren't for a whole society of people telling each other that it's the right thing to do.

The other thing is, religious people have been doing horrible, horrible things all over the world for thousands of years and they're still doing horrible things today. They are the ones making themselves look bad, not anyone else. The image isn't propaganda so much as it's a depiction of what really goes on.