I don't see why that is the case. I'm much more intelligent than a racoon and I have yet to grapple with Rice's Theorem. There is no reason I can think of to believe that Rice's Theorem is a serious constraint on intelligence beyond my own. In general, such an agent isn't particularly interested in proving facts about its own program (at least I can't see why it would care any more than we are interested in proving mathematical properties of our own brains). It is interested in maximizing some objective function, which can transparently be done without thinking much at all about Rice's Theorem (all systems which train neural networks and indeed, even simpler optimization problems, pursue such maximization with nary a thought towards Turing or Rice's Theorems).
