Well, it is not extortion, since it is currently legal.
The Communication Decency Act, which is sort of turned on its head to permit indecent content without liability of the host of the site, provided certain steps are followed.
47 USC § 230 - Protection for private blocking and screening of offensive material http://www.law.cornell.edu/uscode/text/47/230
and specifically under that the following language which immunizes the posting of the information and allows them to voluntarily ( for which they charge) to remove it. Many say this is outrageous, but currently, it's the law:
(c)Protection for “Good Samaritan" blocking and screening of offensive material
(1) Treatment of publisher or speaker No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider.
(2) Civil liability
No provider or user of an interactive computer service shall be held liable on account of— (A)any action voluntarily taken in good faith to restrict access to or availability of material that the provider or user considers to be obscene, lewd, lascivious, filthy, excessively violent, harassing, or otherwise objectionable, whether or not such material is constitutionally protected; or
(B)any action taken to enable or make available to information content providers or others the technical means to restrict access to material described in paragraph (1).