Legal defense instead of offense. IANAL, correct me please.
But to the point of this thread, there is no legal requirement that makes it so a boards fiduciary duty is in conflict with broader moral decisions, nor one that requires them to forget about their humanity when applying their duties as corporate officers.
If they are assholes, its because they are assholes, not because they are required to do so by their obligations to the corporation.
Generally I’m not aware of any civil claim that would let shareholders sue over bad morals.
The claim in the suit is notably that the company failed to disclose the behavior, not that they did the behavior (Target notwithstanding), which mostly agrees with your line of questioning.