I do agree that upside down flags stand for distress, but I have a more general interpretation that it stand for subversion: subversion of government, subversion of morals and subversion of traditionalAmerican ideals.
No disrespect should be shown to the flag of the United States of America; theflag should not be dipped to any person or thing. Regimental colors, state flags, andorganization or institutional flags are to be dipped as a mark of honor. (a) The flag should never be displayed with union down, except as a signal of diredistress in instances of extreme danger to life or property.
來源:The United States Flag:Federal Law Relating to Display and Associated Questions http://www.senate.gov/reference/resources/pdf/RL30243.pdf