You would first have to prove that both a claim of certainty exists and then that is was actually an illusion for example as in the case of morality derived in the absence of God would be. However, if you can do both of these then I would have to agree with the principle you state.
Since I was offering it as a general principle rather than pointing to any specific case thereof I don't actually feel that there's any obligation on my part to "prove" anything.
I'll just go ahead and let you do that for me.