Does the federal law cover "same-sex" harassment?
Absolutely. A case decided by the US Supreme Court on March 4, 1998 involved a male employee working on an off-shore oil rig, who claimed he was the victim of sexual harassment from other male workers. The Supreme Court unanimously held same sex sexual harassment is prohibited under the Federal law, and it does not matter if the same sex harasser was or was not a homosexual.
Harassing conduct need not be motivated by sexual desire. Courts may find an inference of discrimination on the basis of sex if, for example, a female victim is harassed in sex-specific and derogatory terms by another woman, or a male by another male. If it is clear that the harasser is motivated by the sex of the person they are harassing.