Don't take covers so seriously. When did everyone become an American Idol judge?
People on this site have become increasingly critical of covers. Yellowcard played it because they wanted to. The fans liked it. Covers aren't about "doing it better than the original", that can just be a bonus. It's a nice way to pay tribute or introduce an audience to another artist.
Yes but if the cover is legitimately terrible, and they could be performing a song of their own in place of the really terrible cover, the criticism is completely warranted.