The enemy of my friend is...

via Daniel Drezner, guess what these organizations have in common:

• AARP
• AFL-CIO
• Ambulatory Pediatric Association
• American Academy of Pediatrics
• American Civil Liberties Union
• American Academy of Ambulatory Care Nursing
• American Medical Women`s Association
• American Medical Student Association
• American Medical Association
• American Association for the Surgery of Trauma
• American Trauma Society
• American Federation of Teachers
• (list continues, even including letters other than "A")

Answer here