How far do you take this? Kickstarter is a business and needs to make money.
Should it be acceptable for people to Kickstart escort businesses, "legal high" websites, or Amway pyramid schemes? All of those things are legal but are seen by the public as being slimy and taboo. Why would Kickstarter want to associate with these people?
Right, I'm not saying the all-free-speech route is the right answer for Kickstarter; in fact, in my personal opinion, it probably isn't. I'm just saying it's a reasonable question to ask, reasonable people can disagree about the answer, and the whole discussion is orthogonal to whether or not the first amendment obligates them to do anything in particular (since it doesn't).
Should it be acceptable for people to Kickstart escort businesses, "legal high" websites, or Amway pyramid schemes? All of those things are legal but are seen by the public as being slimy and taboo. Why would Kickstarter want to associate with these people?