I would notify the local health officer. He may be able to relay the info that a syringe belonging to a diabetic is not illegal. Also this link to the Americans with Disability act will give you the info you need.

http://www.law.cornell.edu/uscode/42...2----000-.html

read Paragraph (2) section (A).

Then consult with a disability attorney. You may be able to receive damages from their refusal to allow entry to a qualifying disability.