The buttocks in human females thus contain more adipose tissue than in males, especially after puberty. For uncircumcised males, stimulation of the penis in this way comes from the pumping of the foreskin, in which the foreskin is held and slid up and down over the glans, which depending on foreskin length, is completely or partially covered and then uncovered in a rapid motion. Real enema shots or videos of true medical situations may violate privacy laws in some countries. The stigma of being gay or labeled as such has steadily eroded since the Stonewall riots began the modern American gay rights movement in 1969. Transgender pornography features performers who cross-dress for sexual gratification, either for themselves or for their partners. This may relate to fetishes such as voyeurism or cuckolding. The genres of pornography are based on the type of activity featured and the category of participants, for example mateur pornography is a category of pornography that features models, actors or non-professionals performing without pay, or actors for 3d hentai whom this material is their only paid modeling work. The rise of the Internet in the late 1990s and early 2000s similarly changed the way pornography film was distributed and furthermore complicated the censorship regimes around the world and the legal prosecution of obscenity. Softcore gay pornography also exists; it at one time constituted the genre, nude milfs and may be produced as beefcake pornography for heterosexual female and homosexual male consumption. There has been an increase in discussion and portrayal of masturbation in art, popular music, television, films, and literature. Celebrity sex tapes are amateur or professionally-made recordings of gay twinks sex acts, as performed by a celebrity and their partner. Hugo Ohira, director of marketing for Silvercash, rhetorically asks Who does not like spewing their load on a pretty young face? The term soft crush refers to the more common fetish surrounding videos involving inanimate objects or small invertebrates being crushed, while the term hard crush refers to such videos involving larger animals with vertabrae, and arguably more pain-susceptible animals .