Equally, the anti-bard edges help reduce the potency of songs (both beneficial and harmful) sung in the repertoire they go with, not songs which work best for that repertoire.

So if your archenemies are all romantic-preferred bards who usually use romantic, you can counter that by picking Stonehearted, reducing the effectiveness of all songs sung in romantic against you. They, in turn, could choose to try to counter that against you by switching repetoire to epic, tragic, preferred, etc., which wouldn't be their preferred but probably would still be a better choice against specifically you.

Make sense?