Hmm. The catechism itself is written in question and answer format, and then there is a commentary afterward aimed at helping the reader understand what is being discussed.
So let’s pretend that at your brother’s church they are getting together a worship statement and some of the basic tenets of their faith.
The tenets will come from scripture, and some from the early leaders of the faith. Then there will be discussion about the history of the church, and of course there will be historians quoted. Then discussion about the church today, and comments from perhaps the current pastor, and some elders, and then maybe some comments from some of the folks who attend on “what this church means to me”, “what I’ve learned”, etc.
I doubt your brother would be upset by that, or feel that the tenets and beliefs have been ‘negated’ because in talking about the church there are comments in there by "non-religious authors’ like the average guy in the pew. . .
So why is in he in a spittle-flecked nutty over you reading commentary --comments–on the Catholic faith from ‘non-religious authors’ when he apparently isn’t a bit upset that you read comments and listen to him talk about his faith–when he himself isn’t a religious author, either?