Do you feel safe? Are you afraid someone is going to come and threaten your life and liberty? Do you believe that if you were ever threatened, your society is already equipped with stalwart heroes to come and defend you? Do you consider yourself such a stalwart hero?
The core belief here is that only by empowering society to keep guns in the hands of 'the people' can a society truly be free. So the self manufacture of guns is the best way to ensure that freedom. They tend to hold strong beliefs that those in power are only held in check by an armed populous. Otherwise, they claim, what is to stop those in power from taking away the liberty of anyone who displeases them?
For some, the philosophy of freedom is that which you can defend. They tend to view the world in a cold and unforgiving light, and believe that self reliance is the only true chance at prosperity. You likely fall closer to the other end of the spectrum where the strength of society is measured by how well people work together. Civics is a rather broad topic, and we all have our own personal political beliefs. Groups like CATI are just trying to stand up for their own beliefs.