Here's one for the pro-library-degree side: pedophiles and terrorists are calling themselves librarians.
If you need an argument for who can call himself a librarian, someone who works in a library or someone with an MLS or even someone who performs the duties of a librarian, then here are some examples for eliminating the last group from consideration. Apparently, there is a "terrorist librarian" named Nemo who organizes and archives material that could make it easier for some people to kill other people. And another guy, named Philip Thompson, who archived and organized 250,000 images of children that could be used to attract adults who like to fantasize about or have actual sex with children.
The data purist could argue that these guys are special librarians, assisting their customers with finding information, but most people would rightly call them scumbags.
That's the thing about knowledge. It's just a tool to be used by whomever acquires it.
Professional "librarians" should be called that when conform to an ethical code agreed upon by others in the profession and even across other similarly recognized professions. As long as they don't kill people or have sex with kids. Then your privileges get rescinded.