You have to inspect four items to be good at the debate:
1. The book of ethical meat consumption, at your right when entering the convention through the main entrance, the middle one.
2. Inspect the discs near the floor in the music booth to your left when entering the convention through the main entrance, talk to the dinosaur right next to it and he will tell you to listen in some headphones on the wall.
3. Go to the videogame booth, read the manual and play the videogame, use the song to complete the game.
4. In the zone outside, inspect the papers on the activist booth.
Now when you start the debate at 2:30 PM, choose the bottom option