Malpractice won't fly because they are not treating you. Someone who is wrongfully denied a medical certificate can sue to have it issued, provided that they have exhausted all their federal appeal options. While one might sue to force the FAA to issue a medical, suing for damages would be extremely difficult as the federal government is shielded from sues for when its officials are merely exercising their discretion, even if that discretion is proved faulty. You would have to prove some legal of malice, etc, to get past the discretionary function exception to the Federal Tort Claims Act. Suing to force the FAA to provide a medical certificate would be a tough one to win. The courts are going to tend to defer to the FAA, and the regulations are what they are, even if wrong-headed and old-fashioned at times.