You would strictly have to be agnostic about whether there is a teapot in orbit about Mars, but that doesn't mean you treat the likelihood of its existence as on all fours with its non-existence.
Man ville være strengt agnostisk om, hvorvidt der er en tepotte i kredsløb om Mars, men det betyder ikke, at man behandler sandsynligheden for dens eksistens på lige fod med dens ikke-eksistens.