There is a much simpler, if not more time consuming option. When you get to a conversation for which you want to choose the dark side option, simply hit Escape to exit the conversation and swap out Mako for Skadge (if you have him) or Gault before starting the conversation again. Skadge will nab you 100+ affection for darkside choices so it doubles as a good way to gain affection with him since he doesn't really respond well to any of the gifts.