To me an unbiased newspaper is one that confines their opinions to the op/ed section, striving for neutrality/objectivity elsewhere. Are you saying this section shouldn't exist at all? Or that it should be limited to...what, something other than politics?
Editorials are ok if they showcase a variety of viewpoints, even if it's not balanced. If the board collectively decides on a single candidate, I think most people get the impression that this reflects the newspaper as a whole.
Especially endorsing the same party for nearly 50 years to the point where it's expected as a sign of allegience, and non-allegience if they stop. It meant a lot.