No, journalists are not, despite the fervent belief of conservatives, under any obligation to ever be balanced. Balance is nothing but a nice name for the fallacy of the false dichotomy and is absolutely impossible for any human to achieve anyway.
Journalists are beholden to publishing the truth as accurately as they can in the news section, and to respecting their opinions without undue distortion in the opinion pieces. Not only is this their only obligation - it's the absolute most anybody can ever do anyway and even living up to this standard takes a level of discipline very, very few people are capable of sustaining.