I recall that episode, but never understood why it was bad thing if there was a cob planet? Earth is water planet, or dirt planet, with everything destined to be dirt or whatever.
Everything from the mountains down to the atomic structure is on a cob. Maybe you'd end up having Junji Ito tier body horror as they eat and breathe in more cob particles. We'd get Summer on a cob, and Jerry on a cob. Maybe the planet has a god on a cob who will punish them in eternity on the cob, for breaking the laws on the cob, of this world on a cob. Whatever the case, Rick's not willing to take a risk on the cob - as far as he's concerned, there's not so much as one kernel of truth in any criticism of that decision.