The way I read it, Aridas did not claim that ID exists, he only claimed that the concept of ID exists. Which is true for the concept of Santa Claus too.
I hoped that it was pretty clear from what I posted that I understood this, but that the notion of the concept (of anything) existing is unimportant when we are discussing the actuality. In other words, if we're discussing the existence of unicorns, it isn't really helpful if someone comes along and says "the concept of unicorns exists".