Gorshin redeemed his approach to Bele by the way he said "I once heard that on some of your planets people believe they are descended from ...apes."
I thought he played that pause and "apes" line for all the racist intent it was worth, and it worked to establish his true beliefs. Gorshin had range, and not once have I read or heard anyone say they thought of his Riddler while watching the episode. In other words, he was not a one-note performer.
In fact, the episode's other guest star--Lou Antonio-- effectively played the hot-headed political revolutionary on ST, then be just as effective playing a dumb hillbilly on sitcoms like The Monkees