This is a satirical summary of his point.
Many skeptics say that the Flying Spaghetti Monster is imaginary. However, it's impossible to prove that the Flying Spaghetti Monster doesn't exist. Even Richard Dawkins says that you can't prove a negative.You can't make this stuff up.
Therefore, when you say that the Flying Spaghetti Monster is imaginary, you aren't being a true skeptic. Instead, you are expressing "uncritical arrogant dogmatism that would make the most committed fundamentalist blush. And that, my friends, is the irony of the day."