Wow. I'm not going to "justify" any author's credentials to some random person on the internet. Regardless of who they are or what the project is. You only get to know that the authors are the right people for the job because we felt that they were the right people for the job, so we hired them to write the book. If that's not good enough for you, there's plenty of other RPG books out there to spend your money on.
Firstly: you
did give credentials by pointing out that they are POCs. So you not only would “justify” the credentials, but you already had.
Secondly, I’m not sure what angered you about wanting to know about what the authors bring to the table. Especially when “there’s too many white people in Paizo” didn’t phase you.
Thirdly, as a regular Paizo customer and someone who was excited to see this book, I am not just random guy; I am part of your fan base. You want me to buy your book, the hard part is done - getting me to care about Pathfinder and the Mwangi Expanse.
Finally, there have been too many products about “Totally Not Africa” done badly, by various skin tones. I would like something other than “he’s Black, so of course he knows Africa.” I wanted some hype, some reason to be excited about what the authors bring to the table in making a product that I wanted to see.