Arguably the most famous example of the genre is the Taboo series. Various groups within society have considered depictions of a sexual nature immoral, labeling them pornographic, and attempting to have them suppressed under obscenity and other laws, with varying degrees of success. However, sex researchers and adolescent health care professionals have found no evidence for the existence of rainbow parties, and as such attribute the spread of the stories to a moral panic. It may be regarded as taboo or unnatural, and is a criminal offense in some countries, punishable by corporal or capital punishment; by contrast, people also regard anal sex as a natural and valid form of sexual activity that may be as equally fulfilling as any other desired sexual expression. Freud, however, considered such extensions of sexual interest to fall within the range of the normal, unless marked out by exclusivity . A smotherbox has two openings. Ethnic pornography is a genre of pornography that features performers of specific ethnic groups, or depictions of interracial sexual activity. Clothed female, naked male is a genre of erotica featuring one or more nude men and one or more clothed women. Futanari, Hentai females with a penis. It may also involve touching, rubbing, or pinching the nipples gay twink porn or other erogenous zones while masturbating. This is also the case in many relationships not considering themselves as sadomasochistic; mature milfs it is considered to be a part of BDSM if it is practiced purposefully. Pornographic films or sex films are films that present sexually explicit subject matter for the purpose of sexual arousal and erotic satisfaction of the viewer. Through the 1990s, mainstream movie and television hentai porn actors have been more willing to portray homosexuality, as the threat of any backlash against their careers has lessened and society acceptance of gay and lesbian people has increased. As with most forms of sexual activity, anal sex participants risk contracting sexually transmitted infections .