It shall be unlawful for any employer to interfere with, restrain, or deny the exercise of or the attempt to exercise, any right provided under this subchapter.

It shall be unlawful for any employer to discharge or in any other manner discriminate against any individual for opposing any practice made unlawful by this subchapter.

It shall be unlawful for any person to discharge or in any other manner discriminate against any individual because such individual--

(1) has filed any charge, or has instituted or caused to be instituted any proceeding, under or related to this subchapter;

(2) has given, or is about to give, any information in connection with any inquiry or proceeding relating to any right provided under this subchapter; or

(3) has testified, or is about to testify, in any inquiry or proceeding relating to any right provided under this subchapter.