If you read the article it explains its methodology and that it is not limited to the year 2014, which should be evidenced by the reference to Trump supporters, which presumably didn't exist in 2014 because he had not yet announced his candidacy.
> A week ago, a mob stormed the U.S. Capitol in an attempt to block the certification of Joe Biden as the next president. Even though some Capitol Police officers tried to hold back the mob and protect members of Congress, many observers wondered why the rioters did not experience the tear gas and rubber bullets used against the people protesting the killing of George Floyd. As the NAACP tweeted Wednesday, “They’ve killed us for less.”
They literally killed one of the protesters, and not with rubber bullets.
Anyway, the methodology is obviously flawed. They include alternative and mainstream news sources. Only one of these categories is granted "legitimacy", and that one skews far in the other direction.