A conservative pundit answers your question right in the very article you posted.
Originally Posted by your own damn post
Some questioned the use of "bittersweet" during the somber ceremony in Shanksville, Pa., but as Charlie Sperling of the conservative Washington Examiner noted, Biden was speaking at the site where United Flight 93 crashed. The heroic efforts of the plane's 40 passengers and crew members prevented the aircraft from reaching the U.S. Capitol building, believed to be the terrorists' target.
"If you are commemorating Flight 93, that specific event is one of both heroism and tragedy," Sperling noted.
It's hard to be taken seriously when you're so overtly biased that a liberal's blue sky is absolutely, positively gray.