I'm not a lawyer, so I'll wait for what
jespah says about this, but: it seems to me that Kickstarter, IndieGoGo, etc, may be protected by some of the same regulation that protects banks and credit card companies somehow. Financial institutions have to have some sort of equivalent of the safe harbor laws that apply to search engines (that keep them from legal responsibility for search results) for their fees and for managing transactions or VISA would be on the hook every time someone uses one of their cards to pay for an "escort".
I really don't know, and I'd rather not speculate.
Both crowdfunding sites mention that the users have to show they aren't infringing on another's IP.
Indiegogo:
https://www.indiegogo.com/about/terms "User Content ... Each User represents and warrants that its User Content and our use of such User Content will not infringe any third party's intellectual property rights, proprietary rights, privacy rights, confidentiality, rights of publicity or otherwise violate these Terms or applicable law."
Kickstarter:
https://www.kickstarter.com/terms-of-use "11. How We Deal with Copyright Issues ... We reserve the right to delete or disable content alleged to be infringing, and to terminate accounts for repeat infringers."
Plus Kickstarter's Copyright Policy:
https://www.kickstarter.com/help/copyright "Kickstarter has adopted a policy of, in appropriate circumstances, terminating user accounts that are repeat infringers of the intellectual property rights of others. Kickstarter also may terminate user accounts based on even a single infringement."
I encourage you to draw your own conclusions - a Terms of Service document is not going to supercede law or legal precedent, but if Kickstarter and Indiegogo are profiting from infringements and not doing anything to stop that, then I'd say they might want to consult with counsel.