Foreign diplomats cannot be sued in USA under US laws. But can a foreign diplomat sue a US citizen in USA?

My gut says yes.

The most important exception to sovereign immunity is the commercial activity exception, 28 U.S.C. § 1605(a)(2). That section provides three bases on which a plaintiff can sue a foreign state: 1.When the plaintiff's claim is based upon a commercial activity carried on in the U.S. by the foreign state. 2.When the plaintiff's claim is based upon an act by the foreign state which is performed in the U.S. in connection with commercial activity outside the U.S. 3.When the plaintiff's claim is based upon an act by the foreign state which is performed outside the U.S. in connection with commercial activity outside the U.S. and which causes a direct effect in the U.S. For # 2 Question..NO

For a civil matter why not