What is the most serious ethical issue for for society today?
There is probably no one single issue that can be considered the "most" important, as that would relegate certain types of ethical issue to trivial. One could argue, from a Platonic standpoint that one cannot do the good without knowing the good, that intellectual laziness is a root cause of a wide range of ethical problems. Looking for easy solutions rather than really thinking through ethical issues, and often using lack of willingness to examine one's life critically and be honest about one's own ethical flaws, lead to many global forms of injustice. Whether it is the student cheating on papers, the executive overlooking illegal corporate activities, the policeman turning a blind eye to crime, or people walking by unheeding as people are beaten or raped, all have as a root willful ignorance.