Are you born into terrorism?

Really interesting question! In that most "terrorist organizations" come from closely knit cultural groups, and one is born into a given culture, the answer is an oblique "yes". Some examples and discussion are however needed.

There is growing evidence that modern terrorist groups are not so much political action based organizations or even religious cadres, as they are social structures more in line with the format of a street gang. And street gangs are nothing if not cultural, social groupings.

This assertion is reinforced by failures in conducting human intelligence (HUMINT) in terrorist organizations. Simply put, the West has a very difficult time developing covert operatives and Intel sources within Middle-eastern (for instance) terrorist communities -- the reason largely being that the members of the terrorist group are typically from the same culture and quite often from the same geographical micro-community (or village, and they resist inclusion of strangers.

However, most members of a community group that sprouts terrorists are not themselves terrorists. While actual numbers are pretty much impossible to nail down, it seems that even in the most virulent hotbeds of terrorism, only a small minority of the overall population actively participates in terrorist activities, much in the same way that members of a street gang will often all come from a given region, but the majority of dwellers within that region are not themselves street gang members.

That said, I'd have to say that the elements of ones birth regulate entrance into the terrorist community, but do not determine that one "must" enter. You can't get in if you aren't born into the culture, but being born into that culture doesn't mean you're going to become a member of a terrorist organization.