As factual as saying that they were from Vulcan with an ancestor of Mr. Spock commanding them!
Yep.
There was a religious component to it, though.
The Mexican Inquisition was still around (kind of) and Mexico had changed the terms for settlers and wanted all the Protestants to convert, the Jews to covert (or leave) and the Catholics to switch bishops out and change dioceses and come under authority of the (crooked) Mexican bishops.
Not talked about much. But this is why the Catholic dioceses (I’m Catholic) are so convoluted in the SW.
The defenders were 100% faithful Catholics, Protestants, and a couple of Jews.