Did you even read your link? All of it, I mean? Or were you distracted by that pretty red and blue arrow, and you got no further?
These media sources have a slight to moderate liberal bias. They often publish factual information that utilizes loaded words (wording that attempts to influence an audience by using appeal to emotion or stereotypes) to favor liberal causes. These sources are generally trustworthy for information, but may require further investigation. See all Left-Center sources.
Factual Reporting: HIGH
Notes: The Washington Post is an American daily newspaper. It is the most widely circulated newspaper published in Washington, D.C., and was founded on December 6, 1877. The newspaper has won 47 Pulitzer Prizes. This includes six separate Pulitzers awarded in 2008, the second-highest number ever awarded to a single newspaper in one year. Post journalists have also received 18 Nieman Fellowships and 368 White House News Photographers Association awards. The Washington Post has a liberal bias in reporting choices, however they are typically well sourced to credible information. Sometimes they rush stories to be the first to break them, which leads to poor sourcing. This has occurred on a few occasions in 2016. When an error is made the Washington Post responsibly makes corrections. (5/18/2016) Updated (1/12/2017)
So yes, there's a little negative in there, but overall, your source is giving WaPo some pretty high marks.