I don’t think the last comment is doing the same, because I’m speaking one on one to the reader. Here’s what I mean…

(a) As a writer, you ruin your credibility by lumping mass groups…
vs.
(b) Writers are ruining their credibility by lumping mass groups…

In (a) I am speaking directly to the reader. In (b) I would be lumping all writers together and presuming that “all” writers lump mass groups together, when in fact they do not.

To use a real example, instead of saying “millennials have a habit of…” it would be more accurate to go get the data and say “52% of millennials…”

Another one… “Republicans don’t believe in global warming..” — another generalization. Do the work. Go get the numbers. xx% of Republicans don’t believe in global warming.

One is believable and credible — the other is not.

I do agree that it’s easy for anyone to call themselves a journalist, and that whether one is or isn’t a “journalist” doesn’t necessarily speak of quality. There’s tons of good writers that aren’t journalists, and plenty of lousy writers that are.