You can make them parallel adjectives, as in "…, whether tall or short, …":
Everyone, whether unabashedly atheist or staunchly Catholic, speaks with one voice on this issue.
You can make them plural generic nouns:
Everyone, whether unabashed atheists or (staunch) Catholic clergymen/clergy, speaks with one voice on this issue.
Or, in this case, you can make them singular generic:
Everyone, whether unabashed atheist or Catholic cleric, speaks with one voice on this issue.