What they are doing is popularizing the idea of experimentation, and they're doing a very good job of that. The fact that their experiments lack scientific rigor is rather beside the point, particularly since that sort of rigor would make for spectacularly uninteresting television.
It's a fun show that introduces a number of beneficial memes to the public, not least being that claims shouldn't simply be accepted because someone says that something is true. In fact, they go out of the way to have episodes where their *own* results are challenged and reevaluated.
Although it isn't science, it has at its core the same ethos that drives science and strikes me that your objection is tantamount to making the perfect the enemy of the good.