Kickstarter is a private company that can decide what they want to have on their site for whatever reason they want. They have to answer to their customers. If you disagree, don't use Kickstarter.

But the idea that they have to comply with "freedom of speech" or be consistent or anything else doesn't make sense to me. Every store curates it's inventory with whatever rules they deem appropriate. Kickstarter never claimed that any possible piece of content was ok.