Help with (pseudo-)rational film characters

Hi,

I’m currently developing a web-series based around two people who call themselves rationalists, planning to assassinate people in order to bring down the catholic church.

So my fixpoints are that they need sound, or at least compelling, rational argument to justify killing people for “the greater good” (because they are sure the church works very strongly against that). Also, since it’ll be the style of the series, they document themselves while planning their actions. They post encrypted versions of their videos and all data used online and have a mechanism for releasing the keys in case they are caught. Being rational, they know that they will be caught eventually and want to get “their method” out there, hoping to set off some kind of “non-ideological revolution”. Although they know it will probably end badly for them, they are as careful as possible, while trying to not be overly paranoid since it my affect their performance.

Of course they are biased, since they first had the idea of killing the pope, and then they thought of doing so “rationally”. They do see their bias here, though, and try to work around it a bit, but they must come out on the side of pursuing their plans (or the series ends).

There won’t be a real “message” to the series, although they need to make some quite obvious false assumptions (and some personal bias, too, no fridge-stuffing, but rather they are more ideological than they know, in that born-again christian-become-atheist kind of way, occasionally not understanding the difference between what the basic axioms are, and what dogmas are. Also some bipolar disorder and depression might come in handy), so nobody will get stupid ideas. Also I don’t want to be persecuted for providing terror-manuals.

Let me rephrase that: Starting out as a (sloppy) rationalist, what logical fallacies do you have to trip in order to end up on a position that would endorse terrorism?