You're right.  It is rather simple.

a) He actually introduced the possibility of a biased ruling in his court room.

b) He compromised the APPEARANCE of his court room as unbiased, without actually introducing any possibility of a biased ruling in that court room.

Which is it?  It's clearly b). 

Impartiality or partiality are not a measures of optics or appearances, they are measures of actual bias. You are impartial if you can rule without bias. You are partial if you cannot.  Optics is the realm of professionalism, not impartiality.