You and Tom are absolutely correct!
My statement "...of any kind" might have sounded right in my head as I typed, but in retrospect was beyond the scope of what I meant.
A good example of an oath I don't mind is the Boy Scout (is it called the Oath? can't remember. "On my honor, I will do my best..."). It is perfectly voluntary and the person doing the swearing has a good understanding of what it means.