You are right, of course he is not any more a serious candidate than Jessie Jackson was.... but it gets them face time, and opens their issues to public debate.
If he pulls a Perot and runs as an Independent, he could very well be a spoiler for the Republicans. He will have enough support that he will take enough votes from the Republican candidate, perhaps ensuring a victory for the Zero or whoever wins the nomination.
That makes him very dangerous in my book
With one glaring difference you conveniently omitted.
Jesse never even came close to lead in national polls.