Is it proper for a man who did not keep Shabbos to perform Havdallah? Is it halachacly acceptable to perform it for others?
One who is not Shomer Shabbos is still obligated in the mitzvah of havdala. As such, if he understands what he is saying and doing he can also perform it for others. Based on the circumstances, sometimes it is improper to honor such a person with reciting the havdala for others.