What is a 'bona fide' journalist? Journalists are not licensed in the US. If you act in the capacity of a journalist then you are one.
I remember an episode of Law & Order that dealt with exactly that subject. IIRC, it revolved around a biker bar where a college kid was killed over a jacket he shouldn't have been wearing. One of the potential witnesses, a self-described journalist who wrote in biker pubs, could not be forced to testify on what he found because it would damage his sources.
One would think that Acosta and Trump would be best buddies: they're both obnoxious, self-centered bullies. They use the same tactics and techniques to have attention focused on them.