Why should "feces" be used only in scientific journals?
"fecal matter" is used later in the article. They probably just used "poop" in the title to catch more eyes.
And more clicks.
It was a "Poop Culture" article.
Astute observation. Much care is taken when writing headlines and in the case of news organizations with print editions in addition to their web presence, the web headline isn't necessarily the same as what runs in print because of different concerns, e.g. SEO vs journalistic standards.
I'm not saying they should - my point was that you shouldn't expect "scientific" terminology and language from the Washington Post.