An interesting read on moral turpitude and indecent exposure in the context of California's Indecent Exposure law, Penal Code 314. The court particularly notes and holds that:
Exposing oneself in a public place is not necessarily either “lewd” (as required by § 314) or “base, vile and depraved” (as required by our traditional definition of moral turpitude). For example, as the BIA [Board of Immigration Appeal - clarified by myself] and the California courts appear to agree, a sunbather who removes all his clothes to tan on an unoccupied public beach and wakes to find himself surrounded by offended beachgoers has done nothing either lewd or depraved and thus is neither in violation of § 314 nor guilty of a morally turpitudinous act. See Smith, 497 P.2d at 810.
Similarly, the California courts have indicated that they would not uphold a § 314 conviction for urinating in public, because exposure motivated by the need to relieve oneself is not properly classified as “lewd.”
06-70219 9th Circuit Court of Appeals re: Indecent Exposure and Moral Turpitude