It more says that people can be religiously scientific. We're seeing that today, even, where various people chose their favorite scientist "pope" and just believe their proclamations rather than taking pains to understand the underlying science. Obviously, we cannot all be specialists, but ho-boy, my feed is full of people who think they are.
Secularism can cross that threshold, too. People can try to excise religious influence from their decisions, but then actually go too far and actively attack faith. You can maybe tell when the secularism becomes religious when people become
offended by things they proclaim are evidence of religion.
There is a very big difference between a secular society and an atheist society, in practice. "Like a religion" is also being used metaphorically.
Social environment matters. People are not born zealots, they are being indoctrinated.
Partially true. A sufficient number of people go through a phase of their life where they
seek to become zealots. How that manifests will be predictable based on their culture, obviously, but enough people build their own crazy.
Of the people who traveled to heed ISIS's call, you'll find a reasonable percentage had 'normal' upbringings. Obviously, you can find variance if you look closely enough at anything, but they weren't 'indoctrinated' they sought out the indoctrination.