Then perhaps there is no such a thing as a pro photog, it seem that anyone getting a pay check can claim to be a pro without having any credential whatsoever, needing any proof of his skills, need to answer to no-one and is not required to guarantee any level of quality.
That could be part of the problem facing the profession given there is nothing that differentiate them apart from the claims of average Joes.
The problem with saying that, is the work is the proof. People see a photographer's work, and they choose based on previous work. That is the difference from most professions. Get hired as an analyst, developer, draftsman, researcher, teacher, etc. one has almost no way to view the quality of the work. Photographers, pro or amateur, our work is our proof.
I don't see credentials, associations, guilds, or anything outside a college degree more than just a piece a paper someone paid for and it has no basis if they should be in the chosen profession or not. To compare a photographer to someone (doctor, engineer, architect, dentist, etc.) who if they fail, could could kill people, is proposing an extreme comparison that falls short. A pretend photographer may leave a sick feeling in someones gut, but it would hardly kill them. A pretend engineer could kill 1,000s.
These discussions almost seem more like a discussion of the misunderstanding of the definitions of words used. Hate to split hairs but words do have defined meanings. All from merriam-webster.
a: devotee, admirer
b: one who engages in a pursuit, study, science, or sport as a pastime rather than as a profession.
a: Participating for gain or livelihood in an activity or field of endeavor often engaged in by amateurs
b: having a particular profession as a permanent career
c: engaged in by persons receiving financial return
a: expert; especially : one who understands the details, technique, or principles of an art and is competent to act as a critical judge
b: one who enjoys with discrimination and appreciation of subtleties