Ken Ham, and any parent who inculcates such ignorance in children should be locked up. It's child abuse, plain and simple.
That's a little extreme, IMO. Actively exposed as frauds and berated, yes, but locked up? As fired up as this perpetuation of ignorance makes me, I still believe the 1st Amendment guarantees one's right to be willfully ignorant, and if one wants to raise his/her kids that way, it's not the government's place to interfere. (That would be a very slippery slope to walk on...)
Now, on the other hand, if a parent unwittingly paid Ken Ham to educate their kid in science, they might have a good case for a class-action lawsuit for parents to get a full refund on their investment...