Well, Sax is a tricky player around here, it seems. True, the whole scheme of this challenge just happened to be a bit quick, kind of making the game to get going, because Sax believes that the game is going nowhere if it's just discussion without a challenge, or a challenge with discussion, but no votes. Of course, discussion is a vital part into collecting information from others, but deadlines can be an issue because Slacker can randomly choose players to pit each other, and you don't know if that could end up being you.
And as to what H-J said about that match up, there are three possible ways:
Town VS. Town - Guaranteed Town Loss
Town VS. Mafia - 50/50 Chance
Mafia VS. Mafia - Guaranteed Mafia Loss
Still, the example here shows the mafia is being used as a whole, not one mafia group.
But yeah, there are two groups.