My employer conducted an internal investigation regarding a complaint of sexual harassment made by another employee and I was interviewed as part of the investigation. Am I protected from retaliation based on incidents of sexual harassment or inappropriate workplace behavior that I disclosed during the investigation?

Yes. According to the Supreme Court's ruling in Crawford v. Metro Government of Nashville the anti-retaliation provisions of Title VII protect an employee from retaliation based on incidents of sexual harassment that they reported during an investigation by an employer initiated by the complaint of another employee.

The idea here is that employees should not be fearful about retaliation for what they say during an employer's internal investigation, because, the theory goes, if the employer gets full and complete information it will act prudently and rationally to eradicate sexual harassment and discrimination from its workplace.  Obviously, the theory sometimes fails in application and wrongs are done, but the idea is sound and reasonable.