I don't think it should be illegal to print, but can see how Kickstarter employees could see it as advocating violence in the context of it's name and origin.

I think employees would be similarly outraged if someone was crowd funding a comic called "how to mow down leftists" after the Charlottesville car attack.

Again, not illegal, but you could see it as advocating vigilantism and not want it on their platform.

In general, I oppose vigilantism and violence, and think both sentiments are detestable.