Actually I'd suggest that they were subjectively defining there own subset of photography for their own benefit in an act of shameless self promotion as stated in paragraph 2 in the excerpt below.
Your're certainly entitled to your own opinion on it, but you are stating that it is shameless and therefore wrong to "self promote", my opinion on that is, utter nonsense. It's called being in "business" for yourself--------what is wrong with that? They were no doubt trying to put money in their pockests by selling prints just as many may do today. The manifesto was simply a core belief and a passionate one for those practitioners, just like it may be for some today, me included. I do not care for the "fuzzy wuzzies" myself or otherwise turning a photograph into something that does not look like a photograph. IMO, anytime I may post a photograph on the web, I am, in a manner of speaking, promoting "straight" photography in my own right but without the "manifesto", who needs one these days anyway.
"The difference between a very good print and a fine print is quite subtle and difficult , if not impossible, to describe in words."
---AA (The Print)