Apparently WaPo's name for the "Opinion" section is "Perspective" which is somewhat misleading. Also most people reading online won't care to look - I had to go back and look after reading this comment, because it isn't mentioned at all in the headline that this is a biased opinion piece.
Again, you're missing the point. Most publications (newspapers etc. that also publish hard news) indicate that it is an opinion right in the title of the article so that there is no mistaking it.
That is what PostEverything Perspectives is. The description for PostEverything itself on the main page is "The conversation is bigger than you think."
Or as I said above in response to a similar comment:
Mouse over "Perspective" at the top of the page and you will see:
"Perspective: Discussion of news topics with a point of view, including narratives by individuals regarding their own experiences"